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3. For what value of [tex]\(a\)[/tex], [tex]\(4x^4 + 2x^3 - 3x^2 - ax - 28\)[/tex] has [tex]\(-2\)[/tex] as its zero?

A. -3
B. 2
C. -4
D. -2


Sagot :

To determine the value of [tex]\(a\)[/tex] for which the polynomial [tex]\(4x^4 + 2x^3 - 3x^2 - ax - 28\)[/tex] has [tex]\(-2\)[/tex] as a zero, we need to substitute [tex]\(-2\)[/tex] for [tex]\(x\)[/tex] in the polynomial and set the equation equal to zero.

Let's substitute [tex]\(x = -2\)[/tex]:

[tex]\[4(-2)^4 + 2(-2)^3 - 3(-2)^2 - a(-2) - 28 = 0\][/tex]

Step-by-step calculation:

1. Calculate [tex]\(4(-2)^4\)[/tex]:
[tex]\[ 4 \times (-2)^4 = 4 \times 16 = 64 \][/tex]
2. Calculate [tex]\(2(-2)^3\)[/tex]:
[tex]\[ 2 \times (-2)^3 = 2 \times (-8) = -16 \][/tex]
3. Calculate [tex]\(-3(-2)^2\)[/tex]:
[tex]\[ -3 \times (-2)^2 = -3 \times 4 = -12 \][/tex]
4. The constant term is:
[tex]\[ -28 \][/tex]
5. Combine the calculated terms:
[tex]\[ 64 - 16 - 12 - (-2a) - 28 \][/tex]

Combine and simplify the expression:
[tex]\[ 64 - 16 - 12 - 28 + 2a = 0 \][/tex]

6. Sum the constants:
[tex]\[ 64 - 16 - 12 - 28 = 8 \][/tex]

7. Incorporate the remaining terms to solve for [tex]\(a\)[/tex]:
[tex]\[ 8 + 2a = 0 \][/tex]

8. Isolate [tex]\(a\)[/tex] by subtracting 8 from both sides:
[tex]\[ 2a = -8 \][/tex]

9. Finally, solve for [tex]\(a\)[/tex] by dividing both sides by 2:
[tex]\[ a = -4 \][/tex]

Thus, the value of [tex]\(a\)[/tex] is [tex]\(-4\)[/tex].

So the correct answer is:
c) [tex]\(-4\)[/tex]
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