MCQ
$\int \frac{d x}{\sqrt{21+12 x-9 x^2}}=\ldots \ldots \ldots+c$.
- A$\sin ^{-1}\left(\frac{3 x-2}{5}\right)$
- B$3 \sin ^{-1}\left(\frac{3 x-2}{5}\right)$
- ✓$\frac{1}{3} \sin ^{-1}\left(\frac{3 x-2}{5}\right)$
- D$\frac{1}{15} \sin ^{-1}\left(\frac{3 x-2}{5}\right)$