9th grade Algebra help: Best Answer

I need a mind refresher. I learned this almost 5 months ago and I am supposed to do a review.

Please label the steps you did to solve this.
Solve this system- 3x+4y=-36
-x+4y= -16

I remember deep in my mind a combination method, which I would do here if I remembered it. :(

hey man
simultaneous equations

look at the second equation. -2x + 4y = -16
rearrange it. 2x = 4y + 16
divide by 2. x = 2y + 8
you now have an equation in terms of x. substitute this into the first equation ( 3x + 4y = 36)
this turns out as 3 ( 2y + 8) + 4y = -36.
now rearrange this to find y.
10y = -60
now y = -6
put y = -6 into either equation to find x
3x + 4 (-6) = -36 (using first equation)
x = -4

now check through substitution



please note - i wasnt sure with the first equation if it was -3x or 3x.
hope i helped :)

Solve one of the equations for one of the variables.
3x -36 = 4y
3/4x - 9 = y

Substitute y in the second equation.
-2x + 4(3/4x - 9) = -16
-2x + 3x - 36 = -16
x = -16 + 36
x = 20

Substitute x in either equation and solve for y
3(20) - 36 = 4y
24 = 4y
y = 6

-3x + 4y = -36 (x2)
-2x + 4y = -16 (x-3)

-6x + 8y = -72
6x + -12y = 48

(x cancels) -4y = 24
y= -6

-2x + 4(-6) = -16
-2x -24 = -16
-2x = 8
x = -4

I used the basics of simultaneous by multiplying both equations to cancel.