# Math

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How do you solve this by linear combinations?

4x+3y=-8
3x-3y=15

• Math -

L1 : 4x+3y=-8
L2 : 3x-3y=15

Do L1+L2--> 7x=7 so x=1
in L1 4*(1)+3y=-8
3y=-12
y=-4

the couple of solution is(1,-4)

• Math -

How did you get x=1? by pugging it in with the 8 right?

• Math -

No. Add equation 1 (what mk-tintin labels L1) to equation 2, (L2) to obtain
7x +0y = -8+15
7x=7
x=1

• Math -

doing L1+L2-->4x+3x+3y-3y=-8+15
--->7x=7
x=1
do u understand?

• Math -

Oh i was looking at it all wrong alright i understand it a bit better now, doh was plugging in the wrong numbers haha. Sorry.

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