Q. 183.7( 6 Votes )

Find the value of k for which the roots of 9x2 + 8kx + 16 = 0 are real and equal.

Answer :

Given that the quadratic equation 9x2 + 8kx + 16 = 0 roots are real and equal.

Comparing with standard quadratic equation ax2 + bx + c = 0


a = 9 b = 8k c = 16


Thus D = 0


Discriminant D = b2 – 4ac = 0


(8k)2 – 4.9.16 = 0


64k2 – 576 = 0


k2 = 9 taking square root both sides



Thus k = 3 or k = – 3 for which the roots are real and equal.


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