Y

The b in y = ax + b: where the line crosses the y-axis, at the point (0, b).

Precisely: The y-coordinate of the point where a graph meets the y-axis, which is its value at x = 0.

How it works

Put x = 0 into the equation; the y you get is the y-intercept. In y = ax + b the ax part vanishes and b is left.

Examples

• The line y = 2x + 3 has y-intercept 3: it crosses the y-axis at (0, 3).
• For a phone plan costing 200 + 50m rupees, the y-intercept 200 is the fixed charge.
• A line through the origin has y-intercept 0.

Do not confuse: The y-intercept is where the line meets the y-axis; the x-intercept is where it meets the x-axis (where y = 0).

Used in

straight-line graphs, the starting value of a linear relationship, parallel lines (same slope, different intercepts)

Related

slope, constant, parallel lines

From

Class 9 Mathematics, Chapter 2: Introduction to Linear Polynomials