Question

What is the solution to the system of equations--- 4x+4y=-12 3x-4y=-23

Answer 1

So with this type of question, you are expected to solve the systems of equations simultaneously
Let   4x + 4y = -12 ..... (1)
        3x - 4y = -23 ..... (2)

By summing (2) and (1)
⇒ 4x + 3x + 4y + (-4y) = -12 + (-23)
     
                                7x = -35
                 ⇒      7x ÷ 7 = -35 ÷ 7
                 ⇒              x = - 5

By substituting x into (1)
                If  4x + 4y = -12 ..... (1)
      then  4 (-5) + 4y = -12
                    ⇒     4y = -12 + 20
                    ⇒       y = 8 ÷ 4
                    ⇒       y = 2

∴ the solution for the system of equation are x = - 5  ;  y = 2