y = mx + b

Part of the Graphs & Systems section of Coddy's Algebra journey. Lesson 17 of 64.

The equation y = mx + b is called the slope-intercept form of a line. The number m multiplying x is the slope. The number b on its own is the y-intercept, the height where the line crosses the y-axis. Here is an example:

y = 2x + 1

This line crosses the y-axis at (0, 1) and climbs 2 for every step right. You can read both facts from the equation without any calculation.

At x = 0, the term mx equals 0, so y = b. Increasing x by 1 increases y by m. These two facts explain why m is the slope and b is the y-intercept.

Challenge

Medium

Read the slope and the y-intercept from y = 3x - 2, then draw the line.

Try it yourself

y = 3x - 2

Draw the graph

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Graphs & Systems

1The Coordinate Plane

Two Numbers, One Point The Four Quadrants Points on the Axes Mirror Points Recap: The Plane

4Slope-Intercept Form

y = mx + bThe Starting Height Write the Equation Solve for y Draw From Any Form Recap: y = mx + b

7Parallel & Perpendicular

Same Slope, Never Meet The Perpendicular Slope A Right-Angle Line Recap: Two Relations

10Systems by Graphing

Two Lines, One Answer Solve by Drawing Check the Crossing When Lines Never Cross Recap: By Graphing

2From Rule to Line

A Rule Makes Points The Points Line Up On the Line or Not?Between the Dots Recap: Rule to Line

5Point-Slope Form

A Point and a Slope From Two Points Flat or Vertical Through Draw From a Point Recap: Point-Slope

8Function Notation

The Name of a Rule Inputs With Signs Find the Input The Graph of f Recap: f(x)

11Solving Systems Exactly

Substitution Isolate First Elimination Scale, Then Add Three Unknowns Two Numbers, Two Facts Recap: Two Methods