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

Comparing f(x) = 4x2 - 8kx - 9  with ax2+bx+c we get
a=4; b=-8k and c=-9.

Since one root is the negative of the other, let us assume that the roots are p an -p.
Sum of the roots, a+(-a)=-b/a=-(-8k)/4
0=2k
k=0

  • 191

 acc to question the roots of question are alpha and -alpha

then  

alpha + (-alpha) = -b/a = -(-8k) / 4  

                       0 = 2k

                       k = 0 

Hope it helps so thumbs up 

  • 115

 let a & b be the roots of the equation then 

a + b = -b/a

a + (-a) = -( -8x ) / 4

0 = 8x / 4

=> x = 0 

  • 57
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