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Zero (Quadratic Functions)

Zero (Quadratic Functions)

One-page printable reference

See It in Action

Two examples of the idea done right—and one common look-alike that is not right.

EXAMPLE

EXAMPLE

NON-EXAMPLE

Definition

A zero of a quadratic function is a value of x that makes the quadratic equation equal to zero. In other words, it is a solution to the equation ax^2 + bx + c = 0.


The zeros of a quadratic function are the x-intercepts of the graph of the quadratic, meaning the points where the parabola crosses the x-axis. These points represent the values of x where the output of the quadratic function is zero.

Key points about zeros:

  • A quadratic function can have:

    • Two zeros: If the parabola crosses the x-axis at two points.

    • One zero: If the parabola touches the x-axis at exactly one point (the vertex).

    • No zeros: If the parabola does not cross the x-axis at all (the graph is either entirely above or below the x-axis).

2

1

0

The graph of a parabola in the coordinate plane. The parabola crosses the x-axis 2 times, and its x-intercepts are marked with arrows.
The graph of a parabola in the coordinate plane. The parabola crosses the x-axis 1 time at its vertex, and its x-intercept is marked with arrows.
The graph of a parabola in the coordinate plane. It does not cross the x-axis.

Example:

For the quadratic equation x^2 - 5x + 6 = 0, the zeros can be found by factoring:


(x - 2)(x - 3) = 0


So, the zeros are x = 2 and x = 3. These are the values of x where the quadratic equation equals zero, and they represent the points where the graph of the quadratic crosses the x-axis.


In summary, the zeros of a quadratic equation are the values of x that make the quadratic function equal to zero, and they correspond to the x-intercepts of the parabola.

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