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# this is a silly question but

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I have tried to help one of my friends with this problem but the answer key has a different answer than mine...did i do something wrong?

So the problem asks to solve each system using substituition or eliminitation:
I chose substituion.

3x+5y=-3
x+2y= -4/3

1) i tried to isolate the x and i got the equation x=-2y-4/3
2) i plugged the value of x in to the first equation and got y=7
and that is where i went wrong...can somebody explain my mistake to me. Thanks.

Sep 14, 2019

#1
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Solve the following system:
{3 x + 5 y = -3 | (equation 1)
x + 2 y = -4/3 | (equation 2)

Subtract 1/3 × (equation 1) from equation 2:
{3 x + 5 y = -3 | (equation 1)
0 x+y/3 = (-1)/3 | (equation 2)

Multiply equation 2 by 3:
{3 x + 5 y = -3 | (equation 1)
0 x+y = -1 | (equation 2)

Subtract 5 × (equation 2) from equation 1:
{3 x+0 y = 2 | (equation 1)
0 x+y = -1 | (equation 2)

Divide equation 1 by 3:
{x+0 y = 2/3 | (equation 1)
0 x+y = -1 | (equation 2)

Collect results:
x = 2/3         and          y = -1

Sep 14, 2019
#2
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i made a dumb mistake :(

thank you for clearing everything up!!

Nirvana  Sep 14, 2019