Question

Solve the system by substitution.
y = 5x
y = 9x + 8

Answer 1

(-2,-10)

Explanation:

So if y=5x and if y=9x+8 then those should be able to equal each other (substitution):

5x=9x+8

Subtract 5x from both sides:

0=4x+8

Subtract 8 from both sides:

-8=4x

Divide both sides by 4:

x=-2

If x=-2, then we can just plug it back into the first equation:

y=5(-2)

Simplify:

y=-10

Answer 2

x = -2

y = -10

Explanation:

So if y = 5x

Then you can put that in place of the y

5x = 9x + 8

Get the x's all on one side by subtracting

-4x = 8

Divide both sides by -4

x = -2

Then insert x into the first equation, so

y = 5(-2)

y = -10