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JAMB Mathematics 2014 Paper

Question : 12

Total: 47

Find the value of k if y - 1 is a factor of y³ + 4y² + ky - 6

Solution:

Concept:

y - 1

is a factor of a polynomial

f(y)

, then by the factor theorem,

f(1) = 0

Explanation:

Let

f(y) = y^{3} + 4y^{2} + ky - 6

Since

y - 1

is a factor, substitute

y = 1

and set the result equal to zero.

f(1) = (1)^{3} + 4(1)^{2} + k(1) - 6 = 0

1 + 4 + k - 6 = 0

k - 1 = 0

k = 1

Answer:

k = 1

Thus, the correct option is D.

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