Understanding point-slope form
Point-slope form is written as y - y1 = m(x - x1), where m is the slope and (x1, y1) is a known point on the line. This form is derived directly from the definition of slope and is the most natural way to write a line when you already know one point and the steepness.
To convert to slope-intercept form, distribute m and isolate y. For example, y - 2 = 3(x - 1) becomes y = 3x - 1.
y - y1 = m(x - x1)
Point-slope form of a line through (x1, y1) with slope m.