Question

If one root of the quadratic equation 2x2

+ kx + 4 =0 is -2 then the value of k is

(A)12 (B) 6 (C)-6 (D) -12​

Answer 1

Answer:

6 is the right answer

put -2 in the value of x and solve the equation equals to 0

you'll get 6

hope it helps thanks✌

Answer 2

Given :- If one root of the quadratic equation 2x² + kx + 4 =0 is -2 then the value of k is (A)12 (B) 6 (C)-6 (D) -12

Answer :-

we know that, if a is the root of f(x) , then,

• f(a) = 0 .

so,

→ f(x) = 2x² + kx + 4

→ f(-2) = 2(-2)² + k(-2) + 4

→ 2 * 4 - 2k + 4 = 0

→ 2k = 8 + 4

→ 2k = 12

→ k = 6 (B) (Ans.)

Hence, value of k will be 6 .

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