Solve using elimination.
-9x – 9y = 18
-9x - 5y = -18

x=7, y=-9

Step-by-step explanation:

-9x – 9y = 18

-9x - 5y = -18

Multiply the second equation by -1

9x + 5y = 18

Add this to the first equation to eliminate x

-9x – 9y = 18

9x +  5y = 18

        -4y =36

Divide each side by -4

-4y/4 = 36/-4

y = -9

Now find x

-9x -9y = 18

-9(x) -9(-9) = 18

-9x +81 = 18

Subtract 81 from each side

-9x +81-81 =18-81

-9x =-63

Divide each side by -9

-9x/-9 = -63/-9

x=7

x = 7, y = -9

Step-by-step explanation:

Multiply equation (1) by -1 and add to equation (2)

9x + 9y = -18

-9x - 5y = -18

4y = -36

y = -9

-9x - 9(-9) = 18

-9x + 81 = 18

-9x = -63

x = 7

< xcy ≅ < xby

step-by-step explanation:

in δcax and δbax,

so, δcax ≅ δbax (side-angle-side or sas)

since δcax ≅ δbax, we can conclude < acx ≅ < abx

in δacy and δaby,

so, δacy ≅ δaby (side-angle-side or sas)

since δacy ≅ δaby, we can conclude < acy ≅ < aby

now,

< acy ≅ < aby

=> < acx + < xcy ≅ < abx + < xby

=> < acx + < xcy ≅ < acx + < xby   (since < acx ≅ < abx already proved above)

subtracting < acx from both sides, we get

< acx + < xcy -< acx ≅ < acx + < xby -< acx

cancelling out < acx and -< acx from both sides, we get

< xcy ≅ < xby (proved)