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Agenda for Thur sday 11 /29 / 12

Agenda for Thur sday 11 /29 / 12. Target 7a : I can solve linear systems by graphing, substitution, and elimination. Questions on solving using substitution More on Solving Linear Systems Using Substitution Assignment…. Solving Linear Systems Using Substitution.

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Agenda for Thur sday 11 /29 / 12

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  1. Agenda forThursday 11/29/12 Target 7a: I can solve linear systems by graphing, substitution, and elimination. • Questions on solving using substitution • More on Solving Linear Systems Using Substitution • Assignment…

  2. Solving Linear Systems Using Substitution

  3. Solving Linear Systems Using Substitution x = 2y – 6 x – 2y = -6 4x + 6y = 4 Before you can use substitution, x or y needs to be alone in one of the equations. 4(2y– 6) + 6y = 4 8y – 24 + 6y = 4 14y – 24 = 4 +24 +24 14y = 28 14 14 y = 2 Plug 2y – 6 in for x. Solve for y. x = 2(2) – 6 x = -2 Plug 2 in for y. Solve for x. The solution is (-2,2)

  4. Lets try another one together! y = -5x – 12 -5x – y = 12 3x – 5y = 4 Get x or y alone in one of the equations. 3x – 5(-5x– 12) = 4 3x + 25x + 60 = 4 28x + 60 = 4 -60 -60 28x = -56 28 28 x = -2 y = -5(-2) – 12 y = -2 Plug -5x – 12 in for y. Solve for x. Plug -2 in for x. Solve for y. The solution is (-2,-2)

  5. Try these… x = y + 3 x – y = 3 x + 2y = -6 y = -3x – 7 3x + y = -7 -2x + 4y = 0 (y + 3) + 2y = -6 3y + 3 = -6 -3 -3 3y = -9 3 3 y = -3 x = -3 + 3 x = 0 (0,-3) -2x + 4(-3x – 7) = 0 -2x – 12x – 28 = 0 -14x – 28 = 0 +28 +28 -14x = 28 -14 -14 x = -2 y = -3(-2) – 7 y = -1 (-2,-1)

  6. A Word Problem! Last year, you mowed grass and shoveled snow for 12 households. You earned $225 for mowing a household’s lawn for an entire year and $200 for shoveling a household’s walk and driveway for an entire year. You earned a total of $2600 last year. How many households did you mow and shovel for last year? Step 1: Write a system of equations. x is mowing y is shoveling x + y = 12 225x + 200y = 2600 y = -x + 12 Step 2: Solve using substitution. 225x + 200(-x + 12) = 2600 225x – 200x + 2400 = 2600 25x + 2400 = 2600 25x = 200 x = 8 y = -8 + 12 y = 4 8 lawns mowed 4 walks & driveways shoveled

  7. Agenda forThursday 11/29/12 Target 7a: I can solve linear systems by graphing, substitution, and elimination. • Assignment… • Pg. 439-440

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