Question

How do you find the solution of the system of equations `y=3x+7` and `y=x-9`?

Answer 1

We can substitute `y = x-9` in the first equation to get the value of `x`

We get `x - 9 = 3x +7`

Transposing `3x` to the left hand side and `-9` to the right hand side, we get

`x - 3x = 7 + 9`

`-2x = 16`

Dividing both sides by `-2`, we get

`(cancel(-2)x)/cancel(-2) = 16/-2`

`color(green)( x = -8`

Substituting `x=-8` in the second equation, we get

`y = -8 - 9`

`color(green)( y = -17`