Question

how to solve using addition, -5x+6y=-12, 5/4x-4=2y

Answer 1

rearrange the 2nd equation by putting the variables on one side

can you do that?

Answer 2

also you could multiply the 2nd equation by the LCD, which is 4, to get rid of the fraction

Answer 3

Multiply the 2nd equation by 4 and put it in standard form : Ax + By = C

Answer 4

5/4x - 4 = 2y -->(4)
5x - 16 = 8y
now put it in standard form
5x - 16 = 8y (subtract 8y from both sides)
5x - 8y - 16 = 0 (add 16 to both sides)
5x - 8y = 16

now put you equations together...
5x - 8y = 16
-5x + 6y = -12
--------------add

once you add them, what do you get ?

Answer 5

why am I adding 16 to each side...

Answer 6

5x - 8y = 16
-5x + 6y = -12
--------------add
-2y = 4
y = 4/-2
y = -2

now sub -2 in for y in either of the equations to find x
5x - 8y = 16
5x - 8(-2) = 16
5x + 16 = 16
5x = 16 - 16
5x = 0
x = 0/5 = 0

check...
-5x + 6y = -12
-5(0) + 6(-2) = -12
0 - 12 = -12
-12 = -12 (correct)

x = 0 and y = -2

any questions ?

Answer 7

you add 16 to both sides because we want the variables on one side and everything else on the other side. We want the equation in standard form.

Answer 8

anymore questions ?

Answer 9

thanks all.. much appreciation

Answer 10

glad to help :)

Answer 11

i was doing it and got to x=0/5 it confused me.. so i was on the right track... just didn't solv for y yet
thanks so much

Answer 12

you are correct....x = 0/5 which is the same as 0, so x = 0