Linear Functions
Every linear function can be written as y = mx + b, where m is the slope and b is the y-intercept. Drag the sliders below and watch how each piece changes the line.
Slope (m) tells you how much y changes for every one unit x increases — the “rise over run.” A larger m makes the line steeper; a negative m makes it fall from left to right.
Y-intercept (b) is where the line crosses the y-axis — the value of y when x is 0. On the graph, that’s the point the line passes through on the vertical axis, marked here with a dot.
On the SAT, you’ll usually be given two points, a table, or a word problem and asked to find m and b yourself, then use the equation to answer a question — so being able to read slope and intercept at a glance is worth practicing.