To find the equation of a line given the slope and a single point, you need to use the point-slope form of y - y1 = m(x - x1). It is almost identical to the slope-intercept form, but you have to find the point for the y-intercept.
Continue ReadingFor example, if given the point (3, 5) and a line with a slope of 2, plug in the values into the x1 and y1 terms of the equation. Doing this gives you y - 5 = 2(x - 3).
Multiplying the 2 on the right side by both x and -3 simplifies the equation into y - 5 = 2x - 6.
Add 5 to both sides of the equation. This isolates y and changes the term on the right to 2x -1. Thus, the equation for the line in slope-intercept form is y = 2x - 1. The line crosses the y-axis at (0, -1).
The original point is (3, 5). When the numbers are plugged the equation, the equation is 5 = 2(3) -1, which is true.