SOLUTION: i need help soving each system of linear equations bysubstitution -4x+y=6 -5x-y=21

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Question 951997: i need help soving each system of linear equations bysubstitution
-4x+y=6
-5x-y=21
Found 3 solutions by MathLover1, stanbon, macston:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++-4%5Cx+%2B+1%5Cy+=+6%2C%0D%0A++++-5%5Cx+%2B+-1%5Cy+=+21+%29%0D%0A++We'll use substitution. After moving 1*y to the right, we get:
-4%2Ax+=+6+-+1%2Ay, or x+=+6%2F-4+-+1%2Ay%2F-4. Substitute that
into another equation:
-5%2A%286%2F-4+-+1%2Ay%2F-4%29+%2B+-1%5Cy+=+21 and simplify: So, we know that y=-6. Since x+=+6%2F-4+-+1%2Ay%2F-4, x=-3.

Answer: system%28+x=-3%2C+y=-6+%29.

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
help soving each system of linear equations bysubstitution
-4x+y=6
-5x-y=21
--------
Modify::
y = 4x+6
y = -5x-21
-------
Substitute to get:
4x+6 = -5x-21
9x = -27
x = -3
-----
Solve for "y"::
y = 4(-3)+6
y = -6
--------------
Cheers,
Stan H.
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Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
Solve second equation for x
-5x=y+21
x=(y+21)/-5 Substitute for x in first equation.
-4((y+21)/-5)+y=6
.8y+16.8+y=6 Subtract 16.8 from each side.
1.8y=-10.8 Divide each side by 1.8.
y=-6 ANSWER 1: y=-6 Substitute for y in first equation.
-4x+y=6
-4x-6=6
-4x=12
x=-3 ANSWER 2: x=-3
CHECK:
-5x-y=21
-5(-3)-(-6)=21
15-(-6)=21
21=21