Question

System of equations 9x+8y=-19 ; 7x+9y=-12

Answer 1

Answer:

(-3,1)

Step-by-step explanation:

9x+8y=-19

7x+9y=-12

I'll assume the question is to find the solution to these equations.  The solution will be the point (x,y) where the two lines intersect.  The intersection is the one point that satisfies both equations (the smae value of (x,y) works in both.

We can either solve matematically of graph to find the intersection.  I'll do both, and hope the answers are identical.

Matematically

Rearrange either equation to isolate one of the variables (either x or y).  I'll take the second and isolate x:

7x+9y=-12

7x = -9y - 12

x = (-9y - 12)/7

Now use this definition of x in the other equation:

9x+8y=-19

9((-9y - 12)/7) + 8y = -19

(-81y - 108)/7 + 8y = -19

-81y - 108 + 56y = - 133

-25y = -25

y = 1

If y = 1, then:

9x+8y=-19

9x+8(1)=-19

9x = -27

x = -3

The solution is (-3,1)

Graphing

Graph both lines and look for the intersection.  The attached graph shows the lines cross at (-3,1).

The solution, bu both approachjes, is (-3,1)