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Math

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PROBLEM

.pembuat fungsi nol polinomial f(x)=4x4+8x33x27x2f(x)=4 x^{4}+8 x^{3}-3 x^{2}-7 x-2 adalah ...
A. x=2x=-2 atau x=1x=-1 atau x=1/2x=-1 / 2
B. x=2x=-2 atau x=1x=1 atau x=1/2x=-1 / 2
C. x=2x=2 atau x=1x=-1 atau x=1/2x=-1 / 2
D. x=2x=2 atau x=1x=1 atau x=1/2x=-1 / 2
E. x=2x=-2 atau x=1x=1 atau x=1/2x=1 / 2

STEP 1

1. We are given the polynomial function f(x)=4x4+8x33x27x2 f(x) = 4x^4 + 8x^3 - 3x^2 - 7x - 2 .
2. We need to find the roots of the polynomial, i.e., the values of x x for which f(x)=0 f(x) = 0 .
3. We have multiple choice options to evaluate.

STEP 2

1. Use the Rational Root Theorem to identify possible rational roots.
2. Test the possible roots using synthetic division or direct substitution.
3. Determine which option contains the correct roots.

STEP 3

Apply the Rational Root Theorem. The possible rational roots are the factors of the constant term 2-2 divided by the factors of the leading coefficient 44.
Possible rational roots: ±1,±2,±12,±14 \pm 1, \pm 2, \pm \frac{1}{2}, \pm \frac{1}{4} .

STEP 4

Test each possible root by substituting into f(x) f(x) to see if it equals zero.
Test x=2 x = -2 :
f(2)=4(2)4+8(2)33(2)27(2)2 f(-2) = 4(-2)^4 + 8(-2)^3 - 3(-2)^2 - 7(-2) - 2 f(2)=4(16)+8(8)3(4)+142 f(-2) = 4(16) + 8(-8) - 3(4) + 14 - 2 f(2)=646412+142 f(-2) = 64 - 64 - 12 + 14 - 2 f(2)=0 f(-2) = 0 x=2 x = -2 is a root.

STEP 5

Test x=1 x = 1 :
f(1)=4(1)4+8(1)33(1)27(1)2 f(1) = 4(1)^4 + 8(1)^3 - 3(1)^2 - 7(1) - 2 f(1)=4+8372 f(1) = 4 + 8 - 3 - 7 - 2 f(1)=0 f(1) = 0 x=1 x = 1 is a root.

STEP 6

Test x=12 x = -\frac{1}{2} :
f(12)=4(12)4+8(12)33(12)27(12)2 f\left(-\frac{1}{2}\right) = 4\left(-\frac{1}{2}\right)^4 + 8\left(-\frac{1}{2}\right)^3 - 3\left(-\frac{1}{2}\right)^2 - 7\left(-\frac{1}{2}\right) - 2 f(12)=4(116)+8(18)3(14)+722 f\left(-\frac{1}{2}\right) = 4\left(\frac{1}{16}\right) + 8\left(-\frac{1}{8}\right) - 3\left(\frac{1}{4}\right) + \frac{7}{2} - 2 f(12)=14134+722 f\left(-\frac{1}{2}\right) = \frac{1}{4} - 1 - \frac{3}{4} + \frac{7}{2} - 2 f(12)=0 f\left(-\frac{1}{2}\right) = 0 x=12 x = -\frac{1}{2} is a root.

SOLUTION

Based on the tests, the roots are x=2 x = -2 , x=1 x = 1 , and x=12 x = -\frac{1}{2} .
The correct option is:
B. x=2 x = -2 or x=1 x = 1 or x=12 x = -\frac{1}{2}
The correct answer is option B.

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