Question

If (x + 1) is factor of polynomial 2x2 + kx, then the value of k is
(A) - 3
(B) 4
(C) 2
(D) - 2​

Answer 1

Answer:

f(x) = 2x²+ kx

Given,

(x + 1) is factor of f(x)

=> x + 1 = 0

x = -1

Since (x + 1) is factor of f(x), the remainder is 0.

Hence f(x) = 0

Now,

Take LHS as the value of f(x) and RHS as the given polynomial.

=> f(x) = 2x²+ kx

0 = 2x²+ kx

Substitute x as -1 (since given)

=> 0 = 2(-1)²+ k(-1)

0 = 2(1) + (-k)

0 = 2 - k

0 + k = 2

k = 2

Hence, the value of k is 2 (C).

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