If the roots of the quadratic equation $x^2+p x+q=0$ are $\tan 30^{\circ}$ and $\tan 15^{\circ}$,…
If the roots of the quadratic equation $x^2+p x+q=0$ are $\tan 30^{\circ}$ and $\tan 15^{\circ}$, respectively then the value of $2+q-p$ is
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2
-
3
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0
-
1
Solution
$x^2+p x+q=0$
$\tan 30^{\circ}+\tan 15^{\circ}=-p$
$\tan 30^{\circ} \cdot \tan 15^{\circ}=q$
$\tan 45^{\circ}=\frac{\tan 30^{\circ}+\tan 15^{\circ}}{1-\tan 30^{\circ} \tan 15^{\circ}}=\frac{-p}{1-q}=1$
$\Rightarrow-p=1-q$
$\Rightarrow q-p=1 \quad \therefore 2+q-p=3$.
Asked in: JEE Main 2006
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