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WAEC Further Mathematics 2014 Paper

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Question : 5

Total: 40

If

f(x) = 3x^{3} + 8x^{2} + 6x + k

f(2) = 1

, find the value of k.

-67
-61
61
67

Solution:

Concept:

To find the value of

k

, substitute

x = 2

into

f(x)

and use the given condition

f(2) = 1

.

Explanation:

Given:

f(x) = 3x^{3} + 8x^{2} + 6x + k

.

Since

f(2) = 1

, substitute

x = 2

:

f(2) = 3(2^{3}) + 8(2^{2}) + 6(2) + k = 1

Simplify each term:

3(8) + 8(4) + 12 + k = 1

24 + 32 + 12 + k = 1

68 + k = 1

Therefore:

k = 1 - 68 = -67

Answer:

The value of

k

is

-67

.

Correct option: A.

-67

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