Question

Can somebody solve this system equation using addition please?

Answer 1

-4x - 5y = 7

3x + 5y = -14

You can add these two equations together straightaway since the y-terms have opposite coefficients.

-4x - 5y = 7

3x + 5y = -14

+___________

-x - 0 = -7

-x = -7

x = 7

Substitute 7 for x into either of the original equations and solve algebraically to find y.

3x + 5y = -14

3(7) + 5y = -14

21 + 5y = -14

21 = -14 - 5y

35 = -5y

-7 = y

Finally, check work by substituting both x- and y-values into both original equations.

-4x - 5y = 7

-4(7) - 5(-7) = 7

-28 + 35 = 7

7 = 7

3x + 5y = -14

3(7) + 5(-7) = -14

21 - 35 = -14

-14 = -14

Answer:

x = 7 and y = -7; (7, -7).