Question

solve by cross multiplication method x + 2y = -9 , 3x + 4y = -17​

Answer 1

Answer:

x+2y=-9 & 3x+4y=-17.

x+2y+9=0 & 3x+4y+17=0.

For cross multiplication we use,

x/b1c2-b2c1=-y/c1a2-c2a1=1/a1b2-a2b1.

Comparing above two equation with general form, we get,

a1=1, b1=2, c1=9.

a2=3, b2=4, c2=17.

By cross multiplication method,

x/(2×17)-(4×9)=-y/(9×3)-(17×1)=1/(1×4)-(3×2).

x/34-36=-y/27-17=1/4-6.

x/-2=-y/10=1/-2.

Now,

x/-2=1/-2.

1x=-2×-2.

x=4. (Because -×-=+).

and,

-y/10=1/-2.

-(-2)y=10×1.

2y=10.

y=10/2.

y=5.

I think this is your answer.