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how do i solve the linear system using substitution for 4x - y = 5 and 4x + 4y = -4. please solve and show all steps

how do i solve the linear system using substitution for 4x -y = 5
                                                                               4x + 4y = -4
 
show all steps. thank you
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1 Answer

4x + 4y = -4
 
Divide both sides by 4:
 
x + y = -1
 
Subtract y from both sides:
 
x = -y - 1
This (-y -1) is the value of x you can use for substitution.
 
The second equation was:
 
4x - y = 5
 
Now, substitute (-y -1) for x:
 
4(-y -1) - y = 5
 
Remove the parentheses:
 
-4y -4 -y = 5
-5y -4 = 5
 
Add 4 to both sides:
 
-5y = 9
 
Divide both sides by -5:
 
y = -9/5
 
Plug this value for y back into either of the original equations and solve for x:
 
4x + 4y = -4

Divide both sides by 4:

x + y = -1
 
x +  -9/5 = -1
 
Add 9/5 to both sides:
 
x = -1 + 9/5
x = 4/5