Question

If one root of the quadratic equation 2x2

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

Answer 1

Answer:

The required value of k is 6

Step-by-step explanation:

Given :

One root of the quadratic equation 2x² + kx + 4 = 0 is -2

To find :

the value of k

Solution :

Let p(x) = 2x² + kx + 4  

Since -2 is a root of the given quadratic polynomial 2x² + kx + 4 , when we substitute x = -2 the result is zero.  

i.e., p(-2) = 0

Put x = -2,  

2(-2)² + k(-2) + 4 = 0

2(4) - 2k + 4 = 0

8 - 2k + 4 = 0

 12 - 2k = 0

  2k = 12

   k = 12/2

   k = 6

Therefore, the required value of k is 6

Answer 2

Step-by-step explanation:

one root of the quadratic equation 2x 2 + kx + 4 = 0 is -2

The value of k

let p (x) = 2x² + kx + 4

since -2 is a root of the given quadratic polynomial 2x² + kx + 4 , when we substitute x = -2 the results is zero.

put = x = -2

2(-2)²+k(-2)+4=0

2(4)=2k+4=0

8-2k+4=0

12-2k=0

2k=12

k=12/2

k=6