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Solve system 4x - 9y = -21, 4x + 3y = -9.  Give a complete explanation for all your steps!

 Dec 1, 2019
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Solve the following system:
{4 x - 9 y = -21 | (equation 1)
4 x + 3 y = -9 | (equation 2)

 

Subtract equation 1 from equation 2:
{4 x - 9 y = -21 | (equation 1)
0 x+12 y = 12 | (equation 2)

 

Divide equation 2 by 12:
{4 x - 9 y = -21 | (equation 1)
0 x+y = 1 | (equation 2)

 

Add 9 × (equation 2) to equation 1:
{4 x+0 y = -12 | (equation 1)
0 x+y = 1 | (equation 2)

 

Divide equation 1 by 4:
{x+0 y = -3 | (equation 1)
0 x+y = 1 | (equation 2)


x = -3         and           y=1
 

 Dec 1, 2019

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