Question

If x = 4 is a zero of the polynomial 2x2 + kx - 12, then find the value of k.​

Answer 1

Let $p(x)=2x^2 + kx - 12$

We have to find, the value of k.

Solution:

Put x = 4 in the given polynomial P(x)and equate zero.

P(4) = 0

$p(4)=2(4)^2 + k(4) - 12$

⇒ 32 + 4k - 12 = 0

⇒ 4k + 20 = 0

⇒ 4k = - 20

⇒ k = - 5

Thus, the value of k is - 5.

Answer 2

Given :- If x = 4 is a zero of the polynomial 2x2 + kx - 12, then find the value of k.

Solution :-

we know that , if a is a zero of the polynomial p(x) ,

• p(a) = 0 .
• a = 4 (given)

so,

→ p(x) = 2x² + kx - 12

→ p(4) = 2(4)² + k * 4 - 12

→ p(4) = 2 * 16 + 4k - 12

→ p(4) = 32 + 4k - 12

→ p(4) = 20 + 4k

then,

→ p(4) = 0

→ 20 + 4k = 0

→ 4k = (-20)

→ k = (-20/4)

→ k = (-5) (Ans.)

Learn more :-

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