Thread: Precal: finding formula for quadratic function

Find a formula for the quadratic function whose graph has the given properties:

A y-intercept of y = 7 and x-intercepts at x = 1, 4


Help please! i don't know how to find the formula...

Write down an arbitrary quadratic function:

For Example:
y = a(x-b)(x-c)

Fill in the details:

"x-intercepts at x = 1, 4"

y = a(x-1)(x-4)

You do the y-intercept.

it wouldn't be y = (1-b)(4-c) because they're x's?

Originally Posted by sksksk

it wouldn't be y = (1-b)(4-c) because they're x's?

TKHunny is telling you the general form of a quadratic function:

where b and c are the two zeros of the quadratic.

You are applying this to your specific problem where b = 1 and c = 4.

-Dan

ohh... got it. thanks