Question

how to solve x+4y=-9 4x-3y=2 by using elimination method

Answer 1

x + 4y = -9
4x - 3y = 2

you want to get rid of x first because it is the easiest method and requires less work
so you multiply the top equation by -4

-4(x+4y=-9)
-4x -16y = 36
4x -3y = 2
0 - 19y = 38
-19y= 38
y = -2

and solve for x from there.

Answer 2

x + 4y = -9
x + 4(-2) = -9
x -8 = - 9
x = -9 + 8
x = -1, right?

Answer 3

Yes. Good job.