# math

Find all zeros of the function f(x)=16x^3-48x^2-145x-75

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f(x)=16x^3-48x^2-145x-75
f(1) = 16 - 48 - 145 - 75 ≠ 0
f(-1) = -16 - 48 + 145 - 75 ≠0
f(3) ≠ 0
f(-3) ≠ 0
f(5) = 0 , yeah!!! , so x-5 is a factor
using synthetic division by x-5
we have 16x^3-48x^2-145x-75 = (x-5)(16x^2 + 32x - 15)

so you have x = 5 and the two roots of 16x^2 + 32x - 15 = 0

I will leave it up to you to find those two roots, let me know what you get.
hint: they are rational.

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posted by Reiny
2. I got -3/4 and -5/4

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posted by Andrea
3. Good job. You found Reiny's typo.

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