Answer: the "y=mx+b" form (called the slope-intercept form of the equation of a line).
Explanation: Finding the equation for a line is a common problem in geometry and trigonometry. There are two common situations where you are asked to find the equation for a line: either you'll be provided with one point on the line and the slope of the line, or you'll be provided two points on the line.
The "b" value (called the y-intercept) is where the line crosses the y-axis.
So point (x1, y1) is actually at (0, b)
and the equation becomes:
Start with
y − y1 = m(x − x1)
(x1, y1) is actually (0, b):
y − b = m(x − 0)
Which is:
y − b = mx
Put b on other side:
y = mx + b