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