Find the roots of quadratic equation
$4 x^{2} + 9 + 12 x = 81$

-3, 6

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-3, -6

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3, 6

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3, -6

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Solution

The correct option is D 3, -6
$4 x^{2} + 9 - 81 + 12 x = 0$
$4 x^{2} - 72 + 12 x = 0$
$x^{2} - 18 + 3 x = 0$
$(x - 3) (x + 6) = 0$
$x = 3 a n d x = - 6$

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Solve the quadratic equation $4 x^{2} + 12 x + 9 = 81$ by completion of squares method. What is the magnitude of sum of both the roots ?

3

63

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