MCQ
If $y=5 \cos x-3 \sin x$, then $\frac{d^2 y}{d x^2}$ is equal to
  • $-y$
  • B
    $y$
  • C
    $25 y$
  • D
    $9 y$

Answer

Correct option: A.
$-y$
We have, $y=5 \cos x-3 \sin x$
$\Rightarrow \frac{d y}{d x}=-5 \sin x-3 \cos x$
$\Rightarrow \frac{d^2 y}{d x^2}=-5 \cos x+3 \sin x=-y$

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