3.1 Solving Two-Step Equations 1 3x + 7 = –5 3x + 7 = –5 – 7 – 7 LESSON Solving Two-Step Equations EXAMPLE 1 Using Subtraction and Division to Solve Solve 3x + 7 = –5. Check your solution. SOLUTION 3x + 7 = –5 Write original equation. 3x + 7 = –5 – 7 – 7 Subtract 7 from each side. 3x = –12 Simplify. 3x = –12 3 3 = Divide each side by 3. x = –4 Simplify. ANSWER The solution is –4.
3.1 Solving Two-Step Equations 1 3x + 7 = –5 3(–4) + 7 = –5 –5 = –5 LESSON Solving Two-Step Equations EXAMPLE 1 Using Subtraction and Division to Solve Solve 3x + 7 = –5. Check your solution. ANSWER The solution is –4. CHECK 3x + 7 = –5 Write original equation. 3(–4) + 7 = –5 ? Substitute –4 for x. –5 = –5 Solution checks.
3.1 Solving Two-Step Equations 2 – 3 = 1 – 3 = 1 + 3 + 3 = 4 ( ) = (4) LESSON Solving Two-Step Equations EXAMPLE 2 Using Addition and Multiplication to Solve Solve – 3 = 1. Check your solution. x 2 SOLUTION – 3 = 1 x 2 Write original equation. – 3 = 1 x 2 + 3 + 3 Add 3 to each side. = 4 x 2 Simplify. ( ) = (4) x 2 2 2 Multiply each side by 2. x = 8 Simplify. ANSWER The solution is 8.
3.1 Solving Two-Step Equations 2 – 3 = 1 – 3 = 1 1 = 1 LESSON Solving Two-Step Equations EXAMPLE 2 Using Addition and Multiplication to Solve Solve – 3 = 1. Check your solution. x 2 ANSWER The solution is 8. CHECK – 3 = 1 x 2 Write original equation. – 3 = 1 8 2 ? Substitute 8 for x. 1 = 1 Solution checks.
3.1 Solving Two-Step Equations 3 7 – 4y = 19 7 – 4y = 19 – 7 – 7 LESSON Solving Two-Step Equations EXAMPLE 3 Solving an Equation with Negative Coefficients Solve 7 – 4y = 19. Check your solution. SOLUTION 7 – 4y = 19 Write original equation. 7 – 4y = 19 – 7 – 7 Subtract 7 from each side. –4y = 12 Simplify. –4y = 12 –4 –4 = Divide each side by –4. x = –3 Simplify. ANSWER The solution is –3.
3.1 Solving Two-Step Equations 3 7 – 4y = 19 7 – 4(–3) = 19 19 = 19 LESSON Solving Two-Step Equations EXAMPLE 3 Solving an Equation with Negative Coefficients Solve 7 – 4y = 19. Check your solution. ANSWER The solution is –3. CHECK 7 – 4y = 19 Write original equation. 7 – 4(–3) = 19 ? Substitute –3 for y. 19 = 19 Solution checks.
3.1 Solving Two-Step Equations LESSON Solving Two-Step Equations Drum Set You are buying a drum set that costs $495. The music store lets you make a down payment. You can pay the remaining cost in three equal monthly payments with no interest charged. You make a down payment of $150. How much is each monthly payment? You will see how to answer this question by writing and solving a two-step equation. You can solve a two-step equation by using two inverse operations.
3.1 Solving Two-Step Equations 4 495 = 150 + 3p LESSON Solving Two-Step Equations EXAMPLE 4 Writing and Solving a Two-Step Equation Find the monthly payment for the drum set described on Slide 1. SOLUTION Let p represent the monthly payment. Write a verbal model. Total cost of drum set = Amount of down payment + Monthly payment Number of months • 495 = 150 + 3p Substitute.
3.1 Solving Two-Step Equations 4 495 = 150 + 3p 495 = 150 + 3p LESSON Solving Two-Step Equations EXAMPLE 4 Writing and Solving a Two-Step Equation Find the monthly payment for the drum set described on Slide 1. SOLUTION Substitute. 495 = 150 + 3p 495 = 150 + 3p – 150 – 150 Subtract 150 from each side. 345 = 3p Simplify. 345 3p 3 3 = Divide each side by 3. 115 = p Simplify. ANSWER The monthly payment is $115.