Question

How do solve the following linear system?: `y = 4x + 4, 3x - y = -6`?

Answer 1

`x=2` and `y=12`

Explanation:

In two linear equation system, make one variable the subject and substitute that variable in the second equation.

`y = 4x+4` `->` equation 1
`3x-y=-6` `->` equation 2

Substitute `y` from equation 1 to equation 2:

`3x - (4x+4) = -6`

`3x-4x-4 = -6`

`-x-4 = -6`

`-x = -6+4`

`-x = -2`

`x = 2`

Substitute `x=2` in equation 1 or equation 2 to get value of `y`.
Lets take equation 1:

`y=4x+4` `->` equation 1

`y=4(2) + 4`

`y=8+4`

`y=12`

So we get `x=2` and `y=12`

Check the answer:

`3x-y=-6`
`3(2) - 12 = -6`
`6-12=-6`
`-6=-6` `->` Correct