Question

Solve the system of equations below. -3x+6y=9

5x+7y=-49
A. (1,-2)
B.(-2,-7)
C.(-7,-2)
D.(-2,1/2)

Answer 1

Explanation:

By elimination method

-3x+6y=9 Equation 1

5x+7y=-49 Equation 2

multiply Equation 1 by 5, and Equation 2 by 3 so we can cancel out x.

5(-3x+6y=9)

-15x + 30y = 45 Equation 3

3(5x+7y=-49)

15x + 21y = -147 Equation 4

add Equation 3 and Equation 4

-15x + 30y = 45

15x + 21y = -147

51y = -102

y = -2

to get x, substitute the value of y to equation 1 or 2

-3x+6y=9 5x+7y=-49

-3x + 6(-2) = 9 5x + 7(-2) = -49

-3x -12 = 9 5x - 14 = -49

-3x = 21 5x = -35

x = -7 x = -7

C is the correct answer

Answer 2

C

Explanation:

-3x + 6y = 9 5x + 7y = -49

-3x = -6y 5(2y - 3) + 7y = -49

x = 2y - 3 10y - 15 + 7y = -49

17y - 15 = -49

17y = -34 y = -2

-3x + 6(-2) = 9

-3x - 12 = 9

-3x = 21 x = -7

x = -7; y = -2