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Determine the solution to the system of equations

x - 6y + 4z = -12
x + y = 0
2x + 2y = 0

User Gligoran
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3.6k points

1 Answer

2 votes

Answer:

x = 0 , y = 0 , z = -3

Explanation:

Solve the following system:

{x - 6 y + 4 z = -12 | (equation 1)

x + y - 4 z = 12 | (equation 2)

2 x + 2 y + 5 z = -15 | (equation 3)

Swap equation 1 with equation 3:

{2 x + 2 y + 5 z = -15 | (equation 1)

x + y - 4 z = 12 | (equation 2)

x - 6 y + 4 z = -12 | (equation 3)

Subtract 1/2 × (equation 1) from equation 2:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x+0 y - (13 z)/2 = 39/2 | (equation 2)

x - 6 y + 4 z = -12 | (equation 3)

Multiply equation 2 by 2/13:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x+0 y - z = 3 | (equation 2)

x - 6 y + 4 z = -12 | (equation 3)

Subtract 1/2 × (equation 1) from equation 3:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x+0 y - z = 3 | (equation 2)

0 x - 7 y + (3 z)/2 = -9/2 | (equation 3)

Multiply equation 3 by 2:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x+0 y - z = 3 | (equation 2)

0 x - 14 y + 3 z = -9 | (equation 3)

Swap equation 2 with equation 3:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x - 14 y + 3 z = -9 | (equation 2)

0 x+0 y - z = 3 | (equation 3)

Multiply equation 3 by -1:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x - 14 y + 3 z = -9 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Subtract 3 × (equation 3) from equation 2:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x - 14 y+0 z = 0 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Divide equation 2 by -14:

{2 x + 2 y + 5 z = -15 | (equation 1)

0 x+y+0 z = 0 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Subtract 2 × (equation 2) from equation 1:

{2 x + 0 y+5 z = -15 | (equation 1)

0 x+y+0 z = 0 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Subtract 5 × (equation 3) from equation 1:

{2 x+0 y+0 z = 0 | (equation 1)

0 x+y+0 z = 0 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Divide equation 1 by 2:

{x+0 y+0 z = 0 | (equation 1)

0 x+y+0 z = 0 | (equation 2)

0 x+0 y+z = -3 | (equation 3)

Collect results:

Answer: {x = 0 , y = 0 , z = -3

Explanation:

User Andrew
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