Topics from Algebra and PreCalculus. (Key contains solved problems)


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1 Topics from Algebra and PreCalculus (Key contains solved problems) Note: The purpose of this packet is to give you a review of basic skills. You are asked not to use the calculator, except on p. (8) and p.67(70all). Mrs. Shannon Fairfield Warde High School Fairfield, Connecticut
2 ALGEBRA TOPICS LAWS OF EXPONENTS Assume a and b are real numbers and m and n positive integers. (i) (iv) m n m n a a a a ab a b (ii) m m m m m m n n n m (v) a m a a a a m (iii) n a mn PRACTICE PROBLEMS (NO, please!) Simplify: ) c d ) ( a b)( ab )( ab) ) r ( r ) h h 4) Solve for n: ( ) 5n 5 n 5) n n n 6) Write in exponential form (no negative exponents): 6 4 8x y 7) Write in simplest radical form: ) Simplify. Give your answer in exponential form: a a a 9) Using the property of exponents, show that course!) 4 (without the help of a, of 7 9 Solve (algebraic solution!): 0) x 4 8 ) 9x 4
3 FACTORING POLYNOMIALS Perfect Square Trinomials: a ab b ( a b) a ab b ( a b) Difference of Squares: a b ( a b)( a b) Sum of Cubes: a b ( a b)( a ab b ) Difference of Cubes: a b ( a b)( a ab b ) PRACTICE PROBLEMS Factor completely: ) x x 0 ) 4x x 7 ) a 0a 5 4) 4a 4ab b 5 5) 5 6 6) 48 x y x x 6 6 7) x y 8) 6 64 z 9) 8p 0) x( y ) ( y ) ) x 6x 9 4y ) ( x y ) ( x y ) ) 6x 7xy y 4) 4x 8x y 5xy
4 SOLVING POLYNOMIAL INEQUALITIES Example : x 4x 5 0 Solution: x x 5 0 factor mark the zeros; pick a test point to determine the sign of the  5 polynomial in each interval this is called a SIGN CHART! (, 5) PRACTICE PROBLEMS ) x 7x 0x 0 ) x 6x 0 ) ( x 4 x )( x 4) 0 4) x x 0 4
5 PRECALCULUS TOPICS FUNCTIONS You are given a polynomial equation and one or more of its roots. Find the remaining roots. What you need to know: (i) The Remainder Theorem: When a polynomial P(x) is divided by (xa), the remainder is P(a); (ii) Factor Theorem: For a polynomial P(x), (xa) is a factor if and only if P(a)=0; (iii) Use synthetic division when dividing a polynomial by a linear factor; long division will always work; (iv) Odd Function: A function f(x) is odd f(x) = f(x); (v) Even Function: A function f(x) is even f(x) = f(x); Remarks: item (iv) means the graph of the function has rotational symmetry about the origin, and (v) means the graph has reflectional symmetry about the y axis; Find the quotient and the remainder when the first polynomial is divided by the second. No calculators allowed! 4 ) x x 5x ; x ) x x 5x x ; x x ) Determine whether x or x+ are factors of x 4x ) When a polynomial P(x) is divided by x 4, the quotient is. Find P(x). (recall: P(x)=(divisor)x(quotient)+remainder!) x x and the remainder is 5) You are given a polynomial equation and one or more of its roots. Find the remaining roots. 4 x 9x x 9x 4 0; roots: x = , x =. 5
6 Verify algebraically whether the functions are odd or even. 5 6) f ( x ) 5x x 7) hx ( ) x FINDING THE ASYMPTOTES OF A RATIONAL FUNCTION What you need to know: Vertical Asymptote: Set denominator = 0 and solve it. For values of x near the asymptote, the yvalues of the function approach infinity (i.e., the yvalues get increasingly large ) Horizontal or Oblique Asymptote: when the values of x get very large (approach infinity), the yvalues tend to the asymptote. Below is an example of a curve displaying asymptotic behavior: A curve can intersect its asymptote, even infinitely many times. This does not apply to vertical asymptotes of functions. To find the horizontal or oblique asymptote, divide the numerator by the denominator. The asymptote is given by the quotient function. PRACTICE PROBLEMS (No, please!) For the functions below determine: a) the domain; b) the xand yintercepts; c) the vertical, horizontal or oblique asymptotes; and d) whether R(x) is even or odd (show algebraic analysis). x x ) Rx ( ) x x ) rx ( ) x 5x x 4. (explain what happens at x= ) 6
7 8 ) Consider f( x) x. a) is f even or odd? b) explain why there are no vertical asymptotes; c) What is the domain of f? Range? d) Given the equation of its horizontal asymptote. 4) Find a quadratic function f(x) with yintercept  and xintercepts (,0) and,0. RATIONAL ALGEBRAIC EXPRESSIONS AND FUNCTIONS What you need to know: (i) A rational function is a function of the form and qx ( ) 0 for every x. px ( ), where p and q are polynomial functions qx ( ) (ii) To simplify a rational expression, factor both numerator and denominator. Cancel out common factors. (iii) To find the domain of a rational function: solve q(x) = 0. The zeroes of the polynomial q(x) must be excluded from the domain. (iv) To find the zeroes of a rational function: set p(x) = 0 and solve it. The zeros of p(x) are the zeros of the polynomial function (provided they are not also zeros of the denominator q(x)!) In #: Find (a) the domain of each function; and (b) the zeros, if any. No calculators, please! ) gx ( ) x x 9 x 4x 7
8 ( x )( x )( x ) ) gx ( ) x 6x 8 ) hx ( ) x x x x x x Simplify: (attention: just perform the indicated operation ) 4) x 5x 6 x 4 5) x x x x x ( x )( x ) 6) x y x y 4 4 x y Find the constants A and B that make the equation true. FRACTION DECOMPOSITION! x 9 A B 7) x x 6 x x 8
9 Solve the fractional equations. If it has no solution, say so 8) x x x x 5 a 9) a a 6 a EQUATIONS CONTAINING RADICALS Example : Solve x 5 x x 5 x isolate the radical term x x x square both sides 9x 7x 4 0 Solve for x ( x 4)(9x ) 0 x 4 or x these are candidate solutions! 9 Now check each candidate above by plugging them into the original equation. The only possible solution is x 4. PRACTICE PROBLEMS: Solve. If an equation has no solution, say so. (hint: sometimes you may have to square it twice ) ) x 5 x ) x x 4 5 9
10 FUNCTION OPERATIONS AND COMPOSITION; INVERSE FUNCTIONS What you need to know: The composition of a function g with a function f is defined as: h( x ) g( f ( x )) The domain of h is the set of all xvalues such that x is in the domain of f and f(x) is in the domain of g. Functions f and g are inverses of each other provided: f ( g( x )) x and g( f ( x )) x The function g is denoted as f, read as f inverse. When a function f has an inverse, for every point (a,b) on the graph of f, there is a point (b,a) on the graph of f. This means that the graph of f can be obtained from the graph of f by changing every point (x,y) on f to the point (y,x). This also means that the graphs of f and are reflections about the line y=x. Verify that the functions f f ( x ) x and g( x ) x are inverses! Horizontal Line Test: If any horizontal line which is drawn through the graph of a function f intersects the graph no more than once, then f is said to be a onetoone function and has an inverse. Let f and g be functions whose values are given by the table below. Assume g is onetoone with inverse g. X f(x) g(x) ) f( g ()) ) g (4) ) f( g (6)) 4) f ( f ( g())) 5) g( g ()) 6) If f ( x ) x 5 and g( x ) x a, find a so that the graph of f g crosses the yaxis at. 0
11 TRIGONOMETRY What you need to know: Trig values for selected angles: Radians Degrees Sin x Cos x Tan x Und. Key Trig Identities formulas you should know: ( i ) sin cos ( ii ) tan sec ( iv ) cot csc ( v ) sin( x y ) sinx cosy cosx sin y ( vi ) sin( x y ) sinx cosy cosx sin y ( vii ) cos( x y ) cosx cosy sinx sin y ( viii ) cos( x y ) cosx cosy sinx sin y ( ix ) sin sin cos ( x ) cos cos sin cos sin or Without using a calculator or table, find each value: 7. cos( ). sin. cos sin 5. cos 6.sin 6 4
12 7. Find the slope and equation of the line with yintercept = 4 and inclination 45. (the inclination of a line is the angle, where 0 80, that is measured from the positive x axis to the line. If a line has slope m, then m tan ). 8. Find the inclination of the line given the equation: x + 5y = 8 (you ll need a calculator here ) Solve the trigonometric equations algebraically by using identities and without the use of a calculator. You must find all solutions in the interval 0 : 9. sin 0 0. cos x tan x cos x. sin x sinx. cos x cosx. 4. sinx cos x cos x cosx 0 EXPONENTIAL AND LOGARITHMIC FUNCTIONS LOGARITHMS What you need to know Definition of Logarithm with base b: For any positive numbers b and y with b, we define the logarithm of y with base b as follows: x log b y = x if and only if b y
13 LAWS OF LOGARITHMS (for M, N, b0, b ) ( i ) log MN log M log N M ( ii ) logb logb M logb N N ( iii ) log M log N if and only if M N k ( iv ) log M k log M logb M ( ) b b b b b v b M b b The logarithmic and exponential functions are inverse functions. Example: Consider f( x) x and g( x ) log x. Verify that (,8) is on the graph of f and (8,) on the graph of g. In addition, f g x x and g f x x which verifies that f and g are log ( ( )) x x ( ( )) log ( ) indeed inverse functions. Evaluate. (No Calculators, please!) log. log (log 64) 5. 5 x. log log 9 = 5. log 5 6. log Solve for x. 7.log 64 x 8. log ( x 7) 9. log 5(log x ) 0 0. log 6(log (log x )) 0 4
14 . Show that log 4 log 8 log by evaluating the logarithms. Make a generalization based on your findings. Write the given expression as a rational number or as a single logarithm. (Use the laws of logarithms above!). log 8 log5 log 4 4. log48 log7 5. (logm logn log P ) 6. log8 80 log8 5 log r and log 5 s, express the given logarithm in terms of r and s. If log log Solve for x: log ( x 8) log x log 6 Solve (no calculator please!) 0. x 8. 4 x 8. 4 x 6. x x 6 0 (hint: x x x x 6 ( ) ( ) 6 ) Simplify (recall: the notation ln stands for the natural logarithm base e) 4. a) ln e b) e c) e d ) e x ln x ln x ln x Solve for x (answers can be left in terms of e). 5. lnx ln( x ) ln 6. (ln x) 6(ln x) 9 0 4
15 We conclude with the following definition: EXPONENTIAL GROWTH MODEL: Consider an initial quantity Y o that changes exponentially with time t. At any time t the amount Y after t units of time may be given by: kt Y Yoe Where k>0 represents the growth rate and k<0 represents the decay rate. 7. Growth of Cholera: Suppose that the cholera bacteria in a colony grows according to the kt exponential model P P e ). The colony starts with bacterium and doubles in number every o half hour. How many bacteria will the colony contain at the end of 4 hours? 8. Bacteria Growth: A colony of bacteria is grown under ideal conditions in a laboratory so that the population increases exponentially with time. At the end of hours there are 0,000 bacteria. At the end of 5 h there are 40,000 bacteria. How many bacteria were present initially? The halflife of a radioactive element is the time required for half of the radioactive nuclei present in a sample to decay. The next problem shows that the halflife is a constant that depends only on the radioactive substance and not on the number of radioactive nuclei present in the sample. kt 9) Find the halflife of a radioactive substance with decay equation y y e and show that kt the halflife depends only on k. (hint: set up the equation yoe y0. Solve it algebraically for t!) o 0) Using Carbon4 Dating Scientists who do carbon4 dating use 5700 years for its halflife. Find the age of a sample in which 0% of the radioactive nuclei originally present have decayed. 5
16 Limits: ( ) Limit as x approaches c of f(x) equals N LIMIT CONTINUITY Understanding the difference between limits and continuity: Limit is the value (y) that the function APPROACHES as you get close to c (either from one side or from both sides). Continuity implies that the limit exists (from both sides) and that the limit = the value at c! Limit Exists: ( ) ( ) Continuous: ( ) ( ) ( ) ( ) OneSided limit: exists if graph approaches a value from one side: + (right) or (left) Evaluating Limits:. Tables: either from table or by graphing and viewing table looking for values of y approaching the same number. Check one sided limits first and if they are equal the overall limit exists.. Graphically: Check one sided limits (again value of limit is the yvalue or the height of the graph) and if they are equal overall limit exists.. Algebraically: plug in c. If you get a constant then limit exists. Rational functions may need to be simplified first! Properties:. : the limit of a constant A is the constant A think of it as the graph of a horizontal line. Y = A independent of what the x value is.. [ ( ) ( )] ( ) ( ) : you can separate sum and difference of terms.. ( ( )) ( ): you can pull out numeric factors. 4. ( ( )) [ ( )] you can evaluate limit first, then raise your solution to the power. 5. [ ( ) ] ( ) you can evaluate the limit of the numerator and denominator separately then ( ) ( ) evaluate their quotient. Examples: Evaluate the limits: If ( ) {, determine the following: a. ( ) b. ( ) c. ( ) d. Is f continuous? 6
17 8. If ( ) and ( ), determine the following: a. ( ) b. [ ( ) ( )] c. ( ) ( ) 9. Let f(x) be the graph below. Determine the following: a. f() b. ( ) c. ( ) d. ( ) e. ( ) f. ( ) g. ( ) h. f() i. Is f continuous? j. ( ) k. ( ) l. ( ) m. f(4) n. Is f continuous at 4? o. ( ) p. ( ) q. ( ) r. f(0) s. ( ) t. ( ) 7