Question

solve using elimination method
5x+5y=-7
7x-2y=13

Answer 1

ok, lets eliminate y, and find x first:

to eliminate y lets multiply 1st eq by 2 and 2nd eq by -5, to make both Ys cancel each other out once subtracted, so we will have:

10x+10y=-70
-35x+10y=-65

so now we have to subtract coresponding members in both eqs:

45x+0=-5
45x=-5
now divide both sides by a 45 to find x
x=-5/45=-0.111

Answer 2

to find y just substitute it into any of the equations:

5x+5y=-7
5*-0.11111+5y=-7
5y=-7+0.5555
5y=-6.44445
y=-6.44445/5
y = -1.28889
y = -1.289

Answer 3

now lets see if I was correct, by substituting the values into any eq:

5x+5y=-7
5*-0.1111+5*-1.289=
=-7

so I was right and the answers are correct

Answer 4

got it?

Answer 5

that doesn't work for the other equation...you messed up somewhere on top

Answer 6

:/ sorry if I did

Answer 7

but works for me

Answer 8

you didn't cancel out y because you had positive 10y on both equations instead of one positive and one negative so that only gave you the right answer for one equation

Answer 9

ok, so how do I do it?

Answer 10

do the first equation the same but instead of multiplying second equation by -5 multiply it by 5 so you get

10x + 10y = -14
35x - 10y = 65

this way y really is eliminated then you have

45x = 51 so x = 51/45 which is approximately 1.1333....

plug into either equation and solve

7(1.1333) - 2y = 13
or
7.9331 -2y = 13

after solving for y you get y = -2.53345

now check those two values in both equations

Answer 11

ok, thanx mate