Slope-intercept form
SAT glossary · Math
Definition
y = mx+b; the lens that displays the slope m and the y-intercept (0,b). Derived, not memorized, from the constant-rate definition of a linear function by setting x_1=0 in point-slope form.
Slope-intercept form in plain English
Slope-intercept form, y=mx+b, is popular because it puts two of the most useful pieces of information about a line right out in the open: the slope m (how steep the line is and which direction it tilts) and the y-intercept b (the point (0,b) where the line crosses the vertical axis). It's not just a rule to memorize — it actually comes directly from the basic definition of a linear function (a constant rate of change), by taking point-slope form and simply setting x_1=0.
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