Question

Find the x and y intercept for f(x)=x^2-3x-40

Answer 1

To find the y-intercept, simply set the value of x equal to 0, and solve for y, or f(x).

f(x) = 0^2 - 3(0) - 40

f(x) = -40

The y-intercept is -40.

Because this is a 2nd degree polynomial, we cannot find the x-intercepts in one step, and must instead use one of a few different methods.

In this case, we're going to use the quadratic formula:

$\frac{-b +/- \sqrt{b^2 - 4ac} }{2a}$

Plug in the values.

3 +/- √(-3^2 + 160) / 2

3 +/- √169 / 2

3 +/- 13 / 2

(3 + 13) / 2 = 16 / 2 = 8

(3 - 13) = -10 / 2 = -5

The x intercepts are 8, and -5.