Math Problem Statement

Find factors of x^3 - 7x - 6 and x^3 + 12x^2 - 19x = -20

Solution

Let's solve the two questions in the image step by step.

Question 1: Find factors of x37x6x^3 - 7x - 6

We want to factor x37x6x^3 - 7x - 6. To do this, let's first attempt synthetic division or trial and error using rational roots.

Step 1: Check Rational Roots

Possible rational roots are factors of 6-6 (constant term) over factors of 1 (leading coefficient of x3x^3), i.e., ±1,±2,±3,±6\pm 1, \pm 2, \pm 3, \pm 6.

We'll try substituting these values into the equation to check if they are roots.

  • Try x=1x = -1: (1)37(1)6=1+76=0(-1)^3 - 7(-1) - 6 = -1 + 7 - 6 = 0 So, x=1x = -1 is a root.

Step 2: Polynomial Division

Since x=1x = -1 is a root, one factor is x+1x + 1. Now, divide x37x6x^3 - 7x - 6 by x+1x + 1 using synthetic or polynomial division:

Dividing x37x6x^3 - 7x - 6 by x+1x + 1, we get x2x6x^2 - x - 6.

Step 3: Factor the Quadratic

Now, factor x2x6x^2 - x - 6: x2x6=(x3)(x+2)x^2 - x - 6 = (x - 3)(x + 2)

So, the full factorization is: x37x6=(x+1)(x3)(x+2)x^3 - 7x - 6 = (x + 1)(x - 3)(x + 2)

The correct option for Question 1 is C: (x3)(x+2)(x+1)(x - 3)(x + 2)(x + 1).


Question 2: Find factors of x3+12x219x=20x^3 + 12x^2 - 19x = -20

First, rewrite the equation as: x3+12x219x+20=0x^3 + 12x^2 - 19x + 20 = 0

Step 1: Check Rational Roots

The possible rational roots are factors of 2020 over factors of 11, i.e., ±1,±2,±4,±5,±10,±20\pm 1, \pm 2, \pm 4, \pm 5, \pm 10, \pm 20.

  • Try x=1x = 1: 13+12(1)219(1)+20=1+1219+20=14(not a root)1^3 + 12(1)^2 - 19(1) + 20 = 1 + 12 - 19 + 20 = 14 \quad (\text{not a root})

  • Try x=1x = -1: (1)3+12(1)219(1)+20=1+12+19+20=50(not a root)(-1)^3 + 12(-1)^2 - 19(-1) + 20 = -1 + 12 + 19 + 20 = 50 \quad (\text{not a root})

  • Try x=5x = 5: 53+12(5)219(5)+20=125+30095+20=350(not a root)5^3 + 12(5)^2 - 19(5) + 20 = 125 + 300 - 95 + 20 = 350 \quad (\text{not a root})

  • Try x=5x = -5: [ (-5)^3 + 12(-5)^2 - 19(-5) + 20 = -125 + 300 + 95 + 20 = 290 \quad (\text{wrong})

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomial Factorization
Cubic Equations

Formulas

Synthetic division
Factoring cubic polynomials
Rational root theorem

Theorems

Rational Root Theorem

Suitable Grade Level

Grades 9-12