MCQ
Function $f(x) = {{\lambda \sin x + 6\cos x} \over {2\sin x + 3\cos x}}$ is monotonic increasing, if
- A$\lambda > 1$
- B$\lambda < 1$
- C$\lambda < 4$
- ✓$\lambda > 4$
==> $\frac{{(2\sin x + 3\cos x)\,(\lambda \cos x - 6\sin x)}}{{{{(2\sin x + 3\cos x)}^2}}}$
$ - \frac{{(\lambda \sin x + 6\cos x)(2\cos x - 3\sin x)}}{{{{(2\sin x + 3\cos x)}^2}}} > 0$
==> $3\lambda ({\sin ^2}x + {\cos ^2}x) - 12({\sin ^2}x + {\cos ^2}x) > 0$
==> $3\lambda - 12 > 0$ ==> $\lambda > 4.$
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