Warm Up Lesson Presentation Lesson Quiz. Holt Algebra McDougal 1 Algebra 1

Transcription

1 1-3 Warm Up Lesson Presentation Lesson Quiz Holt Algebra McDougal 1 Algebra 1

2 Warm Up Evaluate each expression. 1. ( 7)(2.8) ( 9)( 9)

3 Objective Solve one-step equations in one variable by using multiplication or division.

4 Solving an equation that contains multiplication or division is similar to solving an equation that contains addition or subtraction. Use inverse operations to undo the operations on the variable. Inverse Operations Operation Inverse Operation Multiplication Division Division Multiplication

5 Example 1A: Using Multiplication Solve the equation. 8 = j 3 24 = j Since j is divided by 3, multiply both sides by 3 to undo the division. Check 8 = j substitute 24 for j in the

6 Example 1B: Using Multiplication Solve the equation. n = 2.8 Since n is divided by, multiply both sides by n = 1.8 to undo the division. Check n = substitute 1.8 for n in the

7 Check It Out! Example 1a Solve the equation. Check your answer. p = 10 5 Since p is divided by 5, multiply both sides by 5 p = 50 to undo the division. Check p 5 = substitute 50 for p in the

8 Check It Out! Example 1b Solve the equation. Check your answer. 13 = y 3 39 = y y Check 13 = Since y is divided by 3, multiply both sides by 3 to undo the division. substitute 39 for y in the

9 Check It Out! Example 1c Solve the equation. Check your answer. c = 7 8 Since c is divided by 8, multiply both sides by 8 c = 5 to undo the division. Check c 8 = substitute 5 for c in the

10 Example 2A: Using Division Solve the equation. Check your answer. 9y = 108 y = 12 Since y is multiplied by 9, divide both sides by 9 to undo the multiplication. Check 9y = 108 9(12) substitute 12 for y in the

11 Example 2B: Using Division Solve the equation. Check your answer. 4.8 = v 0.8 = v Since v is multiplied by, divide both sides by to undo the multiplication. Check 4.8 = v 4.8 (0.8) substitute 0.8 for v in the

12 Check It Out! Example 2a Solve the equation. Check your answer. 1 = 4c 4 = c Since c is multiplied by 4, divide both sides by 4 to undo the multiplication. Check 1 = 4c 1 4(4) 1 1 substitute 4 for c in the

13 Check It Out! Example 2b Solve the equation. Check your answer. 0.5y = 10 y = 20 Since y is multiplied by 0.5, divide both sides by 0.5 to undo the multiplication. Check 0.5y = ( 20) substitute 20 for y in the

14 Check It Out! Example 2c Solve the equation. Check your answer. 15k = 75 k = 5 Since k is multiplied by 15, divide both sides by 15 to undo the multiplication. Check 15k = 75 15(5) substitute 5 for k in the

15 Remember that dividing is the same as multiplying by the reciprocal. When solving equations, you will sometimes find it easier to multiply by a reciprocal instead of dividing. This is often true when an equation contains fractions.

16 Example 3A: Solving Equations That Contain Fractions Solve the equation. 5 w = 20 The reciprocal of 5 is. Since w is Check w = 24 5 w = multiplied by 5 by. 5, multiply both sides substitute 24 for w in the 5

17 Example 3B: Solving Equations That Contain Fractions Solve the equation. 3 = 1 z 1 8 The reciprocal of 3 2 = z Check = 8 z multiplied by by substitute is 8. Since z is, multiply both sides for z in the

18 Check It Out! Example 3a Solve the equation. Check your answer. 1 1 = b 4 5 Check 5 4 = b 1 4 = 1 b 5 The reciprocal of multiplied by by substitute 5 4 is 5. Since b is, multiply both sides for b in the

19 Check It Out! Example 3b Solve the equation. 4j = 2 3 j = 1 4j is the same as 4 j. The reciprocal of is. Since j is multiplied by 4 by , multiply both sides

20 Check It Out! Example 3b Continued Solve the equation. 4j = 2 3 Check 4j = 2 3 substitute 1 for j in the

21 Check It Out! Example 3c Solve the equation. 1 w = 102 w = Check w = The reciprocal of multiplied by by. 1 1 is. Since w is, multiply both sides substitute 712 for w in the

22 Example 4: Application Ciro puts 1 4 of the money he earns from mowing lawns into a college education fund. This year Ciro added $285 to his college education fund. Write and solve an equation to find how much money Ciro earned mowing lawns this year. one-fourth times earnings equals college fund Write an equation to represent the relationship. Substitute 285 for c. Since m is divided by 4, multiply both sides by 4 to undo the division. m = $1140 Ciro earned $1140 mowing lawns.

23 Check it Out! Example 4 The distance in miles from the airport that a plane should begin descending, divided by 3, equals the plane's height above the ground in thousands of feet. A plane began descending 45 miles from the airport. Use the equation to find how high the plane was flying when the descent began. Distance divided by 3 equals height in thousands of feet Write an equation to represent the relationship. Substitute 45 for d. 15 = h The plane was flying at 15,000 ft when the descent began.

24 Properties of Equality WORDS NUMBERS ALGEBRA Addition Property of Equality You can add the same number to both sides of an equation, and the statement will still be true. 3 = = = 5 a = b a + c = b + c

25 Properties of Equality WORDS NUMBERS ALGEBRA Subtraction Property of Equality You can subtract the same number from both sides of an equation, and the statement will still be true. 7 = = = 2 a = b a c = b c

26 Properties of Equality WORDS NUMBERS ALGEBRA Multiplication Property of Equality You can multiply both sides of an equation by the same number, and the statement will still be true. = (3) = (3) 18 = 18 a = b ac = bc

27 Properties of Equality WORDS ALGEBRA Division Property of Equality You can divide both sides of an equation by the same nonzero number, and the statement will still be true. NUMBERS 8 8 = 8 8 = = 2 a = b (c 0) a = a c c

28 Lesson Quiz: Part 1 Solve each equation y = = 9q

29 Lesson Quiz: Part 2 7. A person's weight on Venus is about his or 10 her weight on Earth. Write and solve an equation to find how much a person weighs on Earth if he or she weighs 108 pounds on Venus. 9