How do you solve 8x−5y=−46 and 8x+86=y using substitution?

1 Answer
Geoffrey T
May 29, 2018

x=−12
y=−10

Explanation:

You have the value for y. This makes substitution easier.
y=8x+86. Plug that into the other equation 8x−5y=−46
8x−5(8x+86)=−46
Distribute terms and combine like terms.
8x−40x−430=−46
We are left with −32x−430=−46
Solve for x by isolating it.
Add 430 to both sides
−32x=384
Divide both sides by -32
x=−12

Oops. Forgot to solve for y.
Plug the value in for x into one of the equations.
8(−12)−5y=−46
Simplify.
−96−5y=−46
Add 96 to both sides.
−5y=50
Divide both sides by -5
y=−10

Now, check your answers. Plug -12 for x and -10 for y in the second equation.
8(−12)+86=−10
Simplify
−96+86=−10
−10=−10

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