Given that $(x+2)$ and $(2x+3)$ are factors of $f(x) = 6x^3 + px^2 + 4x - q$, we need to find the values of $p$ and $q$, and the roots of $f(x)$.

AlgebraPolynomialsFactor TheoremPolynomial DivisionRoots of PolynomialsCubic EquationsSystems of Equations
2025/4/13

1. Problem Description

Given that (x+2)(x+2) and (2x+3)(2x+3) are factors of f(x)=6x3+px2+4xqf(x) = 6x^3 + px^2 + 4x - q, we need to find the values of pp and qq, and the roots of f(x)f(x).

2. Solution Steps

(a) Since (x+2)(x+2) and (2x+3)(2x+3) are factors of f(x)f(x), we can use the factor theorem. This means that f(2)=0f(-2) = 0 and f(32)=0f(-\frac{3}{2}) = 0.
f(2)=6(2)3+p(2)2+4(2)q=0f(-2) = 6(-2)^3 + p(-2)^2 + 4(-2) - q = 0
48+4p8q=0-48 + 4p - 8 - q = 0
4pq=564p - q = 56 (Equation 1)
f(32)=6(32)3+p(32)2+4(32)q=0f(-\frac{3}{2}) = 6(-\frac{3}{2})^3 + p(-\frac{3}{2})^2 + 4(-\frac{3}{2}) - q = 0
6(278)+p(94)6q=06(-\frac{27}{8}) + p(\frac{9}{4}) - 6 - q = 0
814+94p6q=0-\frac{81}{4} + \frac{9}{4}p - 6 - q = 0
Multiply by 4 to get rid of fractions:
81+9p244q=0-81 + 9p - 24 - 4q = 0
9p4q=1059p - 4q = 105 (Equation 2)
Now we solve the system of equations:
4pq=564p - q = 56
9p4q=1059p - 4q = 105
From Equation 1, q=4p56q = 4p - 56. Substitute this into Equation 2:
9p4(4p56)=1059p - 4(4p - 56) = 105
9p16p+224=1059p - 16p + 224 = 105
7p=119-7p = -119
p=17p = 17
Now substitute p=17p=17 into q=4p56q = 4p - 56:
q=4(17)56=6856=12q = 4(17) - 56 = 68 - 56 = 12
So, p=17p = 17 and q=12q = 12.
(b) Now we know f(x)=6x3+17x2+4x12f(x) = 6x^3 + 17x^2 + 4x - 12. We know that (x+2)(x+2) and (2x+3)(2x+3) are factors. Since f(x)f(x) is a cubic polynomial, it has three roots. We already know two roots are x=2x = -2 and x=32x = -\frac{3}{2}. We want to find the third root.
Since (x+2)(x+2) and (2x+3)(2x+3) are factors, (x+2)(2x+3)=2x2+7x+6(x+2)(2x+3) = 2x^2 + 7x + 6 is a factor of f(x)f(x).
We can perform polynomial division to find the other factor.
(6x3+17x2+4x12)/(2x2+7x+6)=3x2(6x^3 + 17x^2 + 4x - 12) / (2x^2 + 7x + 6) = 3x - 2
So f(x)=(x+2)(2x+3)(3x2)f(x) = (x+2)(2x+3)(3x-2).
Thus, the roots are x=2x = -2, x=32x = -\frac{3}{2}, and x=23x = \frac{2}{3}.

3. Final Answer

(a) p=17p = 17, q=12q = 12
(b) The roots of f(x)f(x) are x=2x = -2, x=32x = -\frac{3}{2}, and x=23x = \frac{2}{3}.

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