Question

Values of k for which equation 9xsq+2kx-1=0has real roots are

Answer 1

Answer :

Given quadratic equation is,

9 x^2 + 2k x - 1 = 0

Comparing this equation with,
a x^2 + b x + c = 0

We get,
a = 9
b = 2k
c = - 1

We know that a quadratic equation equation has real roots if,

b^ - 4 a c > 0
=> (2k)^2 - 4×9×(-1) > 0
=> 4 k^2 + 36 > 0
=> 4 k^2 > - 36
=> k^2 > - 9
=> k >
$\sqrt{ - 9}$

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