How many intercepts does y = x^2 − 5x + 6 have?

1 Answer
Aug 13, 2015

Two x-intercepts and one y-intercept.

Explanation:

You can find this function's x-intercepts by making equal to zero and its y-intercepts by evaluating the function for x=0.

For the x-intercepts, you have

x^2 - 5x + 6 = 0

You can determine how many solutions this quadratic has by calculating its discriminant, Delta, which, for a general form quadratic equation

color(blue)(ax^2 + bx + c = 0)

takes the form

color(blue)(Delta = b^2 - 4ac)

In your case, the discriminant will be

Delta = (-5)^2 - 4 * 1 * 6

Delta = 25 - 24 = color(green)(1)

When Delta>0, the quadratic equation has two distinct real roots that take the form

color(blue)(x_(1,2) = (-b +- sqrt(Delta))/(2a))

In your case, these roots will be

x_(1,2) = (-(-5) +- sqrt(1))/(2 * 1)

x_(1,2) = (5 +- 1)/2 = {(x_1 = (5 + 1)/2 = 3), (x_2 = (5-1)/2 = 2) :}

This means that the function will have two x-intercepts at x=2 and x=3.

The y-intercept will be

y = (0)^2 - 5 * (0) + 6 = 6

The function will intercept the x-axis in the points (2,0) and (3,0), and the y-axis in the point (0, 6).

graph{x^2 - 5x + 6 [-10, 10, -5, 5]}