/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 28 Find the zeros of the function a... [FREE SOLUTION] | 91Ó°ÊÓ

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Find the zeros of the function algebraically. $$ f(x)=x^{3}-4 x^{2}-9 x+36 $$

Short Answer

Expert verified
The zeros of the function \(f(x) = x^{3} - 4x^{2} - 9x + 36\) are x = 3, -2 and 4

Step by step solution

01

Set the Function Equal to Zero

To find the zeros of the function, the function is set equal to zero.\nSo, \(x^{3}-4 x^{2}-9 x+36 = 0\)
02

Factor the Polynomial

To solve the equation, one must factor the polynomial completely. To do this, observe the given cubic equation: \(x^{3}-4 x^{2}-9 x+36 = 0\). It can be noted that it is difficult to perform straightforward factorization here due to the presence of higher polynomial terms. As an alternative approach, one can use Rational Root theorem to determine possible roots of the polynomial. For this polynomial, trial and error can be performed with candidates ±1, ±2, ±3, ±4, ±6, ±9, ±12, ±18, ±36. Through this method, it can be found that the roots of x are 3, -2 and 4.
03

Verification of Roots

The detected roots, 3, -2 and 4, can be verified by substituting these root values back into the original cubic equation.
04

Shorthand Method of Verification

Instead of detailed verification of each root through substitution, a compact way of verification is to factorise using synthetic division and checking for all roots.\nThe cubic function is: \(x^{3}-4 x^{2}-9 x+36 = 0\). Using synthetic division with detected roots, the polynomial can be rewritten as: \((x-3)(x+2)(x-4) = 0\) and it can be observed that the roots are indeed x = 3, -2 and 4.

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