If one zero of the quadratic polynomial f(x)=4x2-8kx-9 . . .

Question : If one zero of the quadratic polynomial f(x)=4x²-8kx-9 is negative of the other, then find the value of k.

Doubt by Ankita

Solution : 

f(x)=4x²-8kx-9

Here 

a=4

b=-8k

c=-9

Let 

α=α

β=-α

Sum of zeroes

α+β=-b/a

α+(-α)=-(-8k)/4

0=2k

0/2=k
0=k

k=0

Hence, the required value of k is 0.