pls help fast as im studiyng for a test, and i cant move...

[thepcnerd]

help pls! im trying to relearn algebra 1-2 before reentering college im studying for my acuplacer and so i will be ready for colege alg, im stuck with a few probs/methods and was wondering if i could get some questions answered and the problems mapped out so i know how there worked, that way i can work them my self... ok

1.) heres the first prob I have

2x+y=-10
-2x-4y=5

im solving for linear sets.

I have so far

2x+y=-10
-2x-4y=4

-2x=4+4y
2(4+4y)+y=-10
8+8y+y=-10
8+9y=-10
-8 8+9y=-10
9y=-10-8>-18
9y=-18





9/9y=9/-18 > -2 cause -2 * 9 = (y)-18 but book im studying from is saying its y=+2

and for x i can tell that the -2 wouldnt work cause -2x(-2)-4x(-2)=4 would come out being 4+8=12, i just want to know what im doing wrong to solve for why, what am i dong wrong to get an -2 and not a poss 2 like i should be, pls help!

 

[mts]

You might find it simpler to solve this system by adding the two equations to eliminate x.

2x+y=-10
-2x-4y=4

Adding the two equations.

2x + (-2x) + y + (-4y) = -10 + 4

-3y = -6

y = 2

Now solve for x using substitution.