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ET 7.2a: Use substitution to solve

ET 7.2a: Use substitution to solve . NO SOLUTION. Solve using elimination. x – y = 5 3x + 2y = 15. Multiply the first equation by 2 so that the coefficient of the y-terms in the system will be opposites. Then, add the equations together and solve for x. 2 x – 2y = 10 3x + 2y = 15.

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ET 7.2a: Use substitution to solve

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  1. ET 7.2a: Use substitution to solve NO SOLUTION

  2. Solve using elimination. x – y = 5 3x + 2y = 15 Multiply the first equation by 2 so that the coefficient of the y-terms in the system will be opposites. Then, add the equations together and solve for x. 2 x – 2y = 10 3x + 2y = 15 2 ( x – y ) = 2 ( 5 ) 3x + 2y = 15 + 5 x = 25 x = 5 Substitute into either of the original equations 5 – y = 5 y = 0 (5, 0)

  3. Solve using elimination. .5x + .3y = .9 .2x - .4y = 1.4 5x + 3y = 9 2x - 4y = 14 Multiply the first equation by 2 & the second equation by -5 so that the coefficient of the x-terms in the system will be opposites. Then, add the equations together and solve for y. 10x + 6y = 18 -10x + 20y = -70 2 ( 5x + 3y ) = 2 ( 9 ) -5(2x - 4y ) = -5 ( 14 ) + 26y = -52 Substitute into either of the original equations y = -2 5x + 3(-2) =9 5x = 15 x = 3 (3, -2)

  4. Solve using elimination. 2x – 3y = 3 -4x + 6y = 6 Multiply the first equation by 2 so that the coefficients of the x-terms in the system will be opposites. Then, add the equations together and solve for y. 4x – 6y = 6 -4x + 6y = 6 2(2x – 3y) = 2(3) -4x + 6y = 6 + 0 = 12 All variables drop out & false statement parallel NO SOLUTION What does that mean?

  5. Solve using elimination. 2x – 3y = 3 -4x + 6y = -6 Multiply the first equation by 2 so that the coefficients of the x-terms in the system will be opposites. Then, add the equations together and solve for y. 4x – 6y = 6 -4x + 6y = -6 2(2x – 3y) = 2(3) -4x + 6y = -6 + 0 = 0 All variables drop out & true statement Same line What does that mean?

  6. ET 7.2a Read the paragraph above ex. 4 on pg 510

  7. 7.2 Assignments • Day 1: 3-5, 7, 17-19, 25, 29, 45, 81 • Day 2: 6, 20, 31-34 (Read the paragraph above ex. 4 on page 510) 49, 53, 55, 82, 85 Fudge  #63 (5 fudge)

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