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8x+10y=-30

-2x+20y=30

 Jul 1, 2018
 #1
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Solve by elimination:
{8 x + 10 y = -30 | (equation 1)
20 y - 2 x = 30 | (equation 2)

Add 1/4 × (equation 1) to equation 2:
{8 x + 10 y = -30 | (equation 1)
0 x+(45 y)/2 = 45/2 | (equation 2)

Divide equation 1 by 2:
{4 x + 5 y = -15 | (equation 1)
0 x+(45 y)/2 = 45/2 | (equation 2)

Multiply equation 2 by 2/45:
{4 x + 5 y = -15 | (equation 1)
0 x+y = 1 | (equation 2)

Subtract 5 × (equation 2) from equation 1:
{4 x+0 y = -20 | (equation 1)
0 x+y = 1 | (equation 2)

Divide equation 1 by 4:
{x+0 y = -5 | (equation 1)
0 x+y = 1 | (equation 2)
x = -5
y = 1

 Jul 1, 2018

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