How do you use end behavior, zeros, y intercepts to sketch the graph of f(x)=(x-4)(x-1)(x+3)?

1 Answer
Mar 29, 2018

end behavior: (-\infty, -\infty), (\infty, \infty)
x-intercepts: (4,0), (1,0), and (-3,0).
y-intercept: (0,12)

Explanation:

If you were to multiply the three factors using the distributive property, you would find that this function is a third degree polynomial because the term with the dependent variable raised to highest power would be the term x^3.

Since the term with the dependent variable raised to the highest power has a positive coefficient (+1) and an odd power (3), end behavior of f(x) when x becomes more negative will move in the direction of -infty and when x becomes more positive will move in the direction of +\infty.
end behavior: (-\infty, -\infty), (\infty, \infty)

To find the zeros, or x-intercepts, of the function, set f(x) = 0 and solve for x. Using the zero product property, we know that f(x) = 0 when any one of the three factors, (x-4), (x-1), or (x+3) is equal to 0. Therefore:
x-intercepts: (4,0), (1,0), and (-3,0).

To find the y-intercept of the function, set x = 0 and solve for f(x):
f(x) = (x - 4)(x - 1)(x + 3)
f(0) = ((0) - 4)((0) - 1)((0) + 3)
f(0) = (- 4)(- 1)(3)
f(0) = 12
y-intercept: (0,12)