Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Indefinite Integration

Question:

$\int\frac{dx}{\sqrt{5-4x-x^2}}$ is equal to

Options:

$\sin^{-1}(\frac{x+2}{3})+C$: C is an arbitrary constant

$\frac{1}{3}\sin^{-1}(\frac{x+2}{3})+C$: C is an arbitrary constant

$3\sin^{-1}(\frac{x+2}{3})+C$: C is an arbitrary constant

$\frac{1}{3}\sin^{-1}(x+2)+C$: C is an arbitrary constant

Correct Answer:

$\sin^{-1}(\frac{x+2}{3})+C$: C is an arbitrary constant

Explanation:

The correct answer is Option (1) → $\sin^{-1}(\frac{x+2}{3})+C$: C is an arbitrary constant

$I=\int \frac{dx}{\sqrt{5-4x-x^{2}}}$

$5-4x-x^{2}=9-(x+2)^{2}$

$I=\int \frac{dx}{\sqrt{9-(x+2)^{2}}}$

$\int \frac{dx}{\sqrt{a^{2}-(x-c)^{2}}}=\sin^{-1}\!\left(\frac{x-c}{a}\right)+C$

$\Rightarrow I=\sin^{-1}\!\left(\frac{x+2}{3}\right)+C$

$\sin^{-1}\!\left(\frac{x+2}{3}\right)+C$