Question

If one root of the quadratic equation 2x2 + kx + 1= 0 is -1/2 , then the value of k is​

Answer 1

Answer:

–1

Step-by-step explanation:

The equation is: 2x² + kx + 1 = 0

Let the another root be Ā.

So, Ā×(–1/2)= 1/2

=>Ā = 1/2×(–2/1)

=> Ā = –1

Now, Ā + (1/2) = –k/2

=> –1+(1/2)=– k/2

=>–1/2 = –k/2

=>k = 1

Answer 2

Answer:

k=3 HOPE IT HELPS YOU

Step-by-step explanation:

We know

addition of roots = -b/a

multiplication of roots = c/a

$2x^2+kx + 1=0$

a = 2

b = k

c = 1

One root = -1/2

Other root = ?

Let other root = x

addition of roots = -b/a

-1/2 + x = -k/2

x = -k/2 + 1/2 equation 1

Now,

Product of roots = c/a

-1/2 * x = 1/2

$\frac{-1}{2} *x= \frac{1}{2} \\\\x = \frac{1*2}{2 * (-1)} \\x = 2/-2\\x = (-1)$

Now putting value of x = (-1) in equation 1

(-1) = -k/2 + 1/2

(-1) - 1/2 = -k/2

 $\frac{-2-1}{2} = \frac{-k}{2} \\\frac{-3}{2} = \frac{-k}{2}$

-3 = -k

k = 3