y-intercept

Definition: The y-intercept of a function is the point at which the function crosses the y-axis.

Rules:

The y-axis is also the line x=0. So substituting x=0 into the function gives the y-intercept.
by definition, a function is single-valued. This means that a function can have at most one y-intercept.

Example: Find the y-intercept of the quadratic function f(x)= x^2+2x-1

Substitute x=0 into the function: f(0)=3 \cdot 0^2+2 \cdot 0-1 =-1

So the y-intercept is: -1 .

That is, the point where this function crosses the y-axis is: (0,-1).