Question

solving systems by elimination PLEASE HELP

3x-y=2
-8x+2y=4

i multiplied 3x-y=2 by 2 and got 6x-2y=4

so then i subtracted the two equations
6x-2y=4
-8x+2y=4
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-2x-=0

are you suppose to add 4 + 4 or subtract? i know the answer to the problem is (-4,-14)

Answer 1

You add the 4. Your new equation would be -2x=8

Answer 2

don't we subtract for this equation? that's what i'm confused at.

Answer 3

or does it vary only by each individual sign next to the number?

Answer 4

The elimination method is also called the addition method. I think you're confused because of the -8x . When you do the problem, you add 6x +(-8x) which still equals -2x.

Answer 5

oh, but how would we know when to add or subtract for each equation?
i was using the negative in -8 as a reason to subtract the whole equation

Answer 6

You will always add. If you don't believe me, check your answer. If my equation of -2x=8 is correct, x=-4. Plug -4 back into one of the original equations. You will get 14. Try another problem and add the terms.

Answer 7

-14 I meant.

Answer 8

thank you so much
so is it that we always add the last number?

Answer 9

Yes, you will add every like term.

Answer 10

ahhhh, thank you!