Question 976117: Solve the system of 2 equations and 2 unknowns using the echelon method.
-4x - 5y = 15
-2x + 2y = -6
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Thanks.
Answer by Cromlix(4381)   (Show Source):
You can put this solution on YOUR website! Hi there,
Start with the given system of equations:
system:
-4x - 5y = 15
-2x + 2y = -6
Now you have to change the 'x' values
or the 'y' values to equal values, but
opposite signs.
Here we will multiply the lower set by -2
-4x - 5y = 15
-2x + 2y = -6 (x -2)
-4x - 5y = 15
4x - 4y = 12
Add the left parts of the equation together,
then the right parts.
(-4x - 5y) + (4x - 4y) = 15 + 12
The 'x' values vanish (-4x + 4x = 0)
-9y = 27
Divide both sides by -9
y = -3
Substitute y = -3 into
-4x - 5y = 15
-4x -5(-3) = 15
-4x = 15 - 15
-4x = 0
x = 0
{0,-3)
Hope this helps:-)
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