Question

How do you write an equation of a line parallel to y=3 passing through P(-2,4)?

Answer 1

`y=4`

Explanation:

Your line, `y=3` is a horizontal line passing through `3` (on the y axis). A line parallel to this one has to be again horizontal but this time passing through `4`, i.e. `y=4`.

A somewhat more rigorous approach would be to say that the slope `m` of `y=3` is zero so using the relationship:
`y-y_0=m(x-x_0)`
you get:
`y-4=0(x+2)`
`y=4`