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15. Use elimination to solve the systems of equations. -7x - 5y = -5 5x + 5y =-5A. (0,1) C. (0,-1) B. (-5,6) D. (5.-6)

1 Answer

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We are given to linear equations which are

-7x - 5y = -5 --------------- equation 1

5x + 5y = -5 ---------------- equation 2

Both equation 1 and 2 can be solve simultaneously using the elimination method

Let us eliminate y first

We are eliminating y because it has the same value in both equations

Add equation 1 and equation 2 together

-7x + 5x - 5y + 5y = -5 + (-5)

-2x + 0y = -5 - 5

-2x + 0 = -10

-2x = -10

Divide both sides by -2

-2x/-2 = -10/-2

x = 10/2

x = 5

To calculate y put x = 5 in equation 1

-7x - 5y = -5

since y x - 5

-7(5) - 5y = -5

-35 - 5y = -5

Collect the like terms

-5y = -5 + 35

-5y = 30

Divide both sides by -5

-5y/-5 = 30/-5

y = -6

x = 5 and y = -6

(5, -6)

The answer is option D

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