Definition: An x-intercept of a function is a point at which the function crosses the x-axis.

Rules:

  • x-intercepts are called roots.
  • The x-axis is also the line y=0. So substituting y=0 and solving for x gives x-intercepts.

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

Substitute y=0 into the function: 0= x^2-x-2
To solve this, we use the quadratic formula. The solutions are: x_1=2    and    x_2=-1
That is, this function crosses the x-axis at 2 points: (2,0) and (-1,0).

  

 


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Page last modified on March 14, 2008, at 02:26 AM