You may want to review slope-intercept form first.

Suppose you have to find the equation of the line through (2,
−4) with slope 2 ⁄ 3. (If the 2 were a
0, you'd already know how to do this.) The answer is *y* =
(2 ⁄ 3)(*x* − 2) − 4. In
general, you want *y* = (slope) (*x* +
(*x*-coordinate with the sign switched)) +
(*y*-coordinate).

Be careful *always* to switch the sign of
the *x*-coordinate and *never* of
the *y*-coordinate.