If the equation $x^{2} + b x + 4 = 0$ has equal roots then find the value of $b$ .

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Solution

The Equation is $x^{2} + b x + 4 = 0$ .
We know that for the quadratic equation having equal roots the discriminant is zero.
Therefore, $D = b^{2} - 4 a c = 0$
Here, $a = 1, b = b, c = 4$
Now putting above values in the discriminant we get,
$D = b^{2} - 4 \times 1 \times 4 = 0$
$\Rightarrow b^{2} = 16$
$\Rightarrow b = - 4, + 4$

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