Question

How do you write an equation in standard form for a line passing through (2, 1) and is perpendicular to x = –2?

Answer 1

`x=-2` represents a vertical line so that a perpendicular line to it will be a perfectly horizontal line passing through `(2,1)`.
A perfectly horizontal line has slope `m=0` (it is not increasing nor decreasing) so you can use your relationship:
`y-y_0=m(x-x_0)` with `m=0` giving:
`y-1=0(x-2)`
So your line has equation: `color(red)(y=1)`