The problem asks to find one root of the cubic equation $x^3 + 2x - 3x^2 - 6 = 0$ from the given options: $1, -1, -3, 3$.

AlgebraPolynomial EquationsCubic EquationsRoot FindingFactorization
2025/3/20

1. Problem Description

The problem asks to find one root of the cubic equation x3+2x3x26=0x^3 + 2x - 3x^2 - 6 = 0 from the given options: 1,1,3,31, -1, -3, 3.

2. Solution Steps

We can rewrite the equation as:
x33x2+2x6=0x^3 - 3x^2 + 2x - 6 = 0
Now, we test each of the given options to see which one satisfies the equation.
Option 1: x=1x = 1
(1)33(1)2+2(1)6=13+26=60(1)^3 - 3(1)^2 + 2(1) - 6 = 1 - 3 + 2 - 6 = -6 \neq 0
So, x=1x = 1 is not a root.
Option 2: x=1x = -1
(1)33(1)2+2(1)6=1326=120(-1)^3 - 3(-1)^2 + 2(-1) - 6 = -1 - 3 - 2 - 6 = -12 \neq 0
So, x=1x = -1 is not a root.
Option 3: x=3x = -3
(3)33(3)2+2(3)6=273(9)66=272766=660(-3)^3 - 3(-3)^2 + 2(-3) - 6 = -27 - 3(9) - 6 - 6 = -27 - 27 - 6 - 6 = -66 \neq 0
So, x=3x = -3 is not a root.
Option 4: x=3x = 3
(3)33(3)2+2(3)6=273(9)+66=2727+66=0(3)^3 - 3(3)^2 + 2(3) - 6 = 27 - 3(9) + 6 - 6 = 27 - 27 + 6 - 6 = 0
So, x=3x = 3 is a root.
Alternatively, we can try to factor the polynomial.
x33x2+2x6=0x^3 - 3x^2 + 2x - 6 = 0
x2(x3)+2(x3)=0x^2(x - 3) + 2(x - 3) = 0
(x2+2)(x3)=0(x^2 + 2)(x - 3) = 0
The roots are x=3x = 3 and x2=2x^2 = -2 which gives x=±i2x = \pm i\sqrt{2}.
The only real root from the options is x=3x = 3.

3. Final Answer

3

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