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

Question

how do i solve the linear system using substitution for 4x -y = 5

                                                                               4x + 4y = -4

 

show all steps. thank you

Answer 1

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