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Match List-I with List-II

List-IList-II
IntegralSolution: C is an arbitrary constant
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(A) ∫dxx2+25\int \frac{dx}{x^2 + 25}(I) 110log⁡∣5+x5−x∣+C\frac{1}{10} \log \left\vert \frac{5 + x}{5 - x} \right\vert + C
(B) ∫dxx2−25\int \frac{dx}{x^2 - 25}(II) log⁡∣x+x2−25∣+C\log \vert x + \sqrt{x^2 - 25}\vert + C
(C) ∫dx25−x2\int \frac{dx}{25 - x^2}(III) 15tan⁡−1(x5)+C\frac{1}{5} \tan^{-1} \left( \frac{x}{5} \right) + C
(D) ∫dxx2−25\int \frac{dx}{\sqrt{x^2 - 25}}(IV) 110log⁡∣x−5x+5∣+C\frac{1}{10} \log \left\vert \frac{x - 5}{x + 5} \right\vert + C

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 2

Standard integral formulas with a=5a = 5 (since 25=5225 = 5^2):

∫dxx2+a2=1atan⁡−1(xa)+C\int \frac{dx}{x^2 + a^2} = \frac{1}{a}\tan^{-1}\left(\frac{x}{a}\right) + C

∫dxx2−a2=12alog⁡∣x−ax+a∣+C\int \frac{dx}{x^2 - a^2} = \frac{1}{2a}\log\left|\frac{x-a}{x+a}\right| + C

∫dxa2−x2=12alog⁡∣a+xa−x∣+C\int \frac{dx}{a^2 - x^2} = \frac{1}{2a}\log\left|\frac{a+x}{a-x}\right| + C

∫dxx2−a2=log⁡∣x+x2−a2∣+C\int \frac{dx}{\sqrt{x^2 - a^2}} = \log\left|x + \sqrt{x^2 - a^2}\right| + C


(A) ∫dxx2+25\int \frac{dx}{x^2 + 25}, with a=5a = 5:

=15tan⁡−1(x5)+C⟶(III)= \frac{1}{5}\tan^{-1}\left(\frac{x}{5}\right) + C \quad \longrightarrow \text{(III)}


(B) ∫dxx2−25\int \frac{dx}{x^2 - 25}, with a=5a = 5:

=12(5)log⁡∣x−5x+5∣+C= \frac{1}{2(5)}\log\left|\frac{x - 5}{x + 5}\right| + C

=110log⁡∣x−5x+5∣+C⟶(IV)= \frac{1}{10}\log\left|\frac{x-5}{x+5}\right| + C \quad \longrightarrow \text{(IV)}


(C) ∫dx25−x2\int \frac{dx}{25 - x^2}, with a=5a = 5:

=12(5)log⁡∣5+x5−x∣+C= \frac{1}{2(5)}\log\left|\frac{5 + x}{5 - x}\right| + C

=110log⁡∣5+x5−x∣+C⟶(I)= \frac{1}{10}\log\left|\frac{5+x}{5-x}\right| + C \quad \longrightarrow \text{(I)}

Note: In (B), x2x^2 comes first → (x−a)(x-a) on top. In (C), a2a^2 comes first → (a+x)(a+x) on top.


(D) ∫dxx2−25\int \frac{dx}{\sqrt{x^2 - 25}}, with a=5a = 5:

=log⁡∣x+x2−25∣+C⟶(II)= \log\left|x + \sqrt{x^2 - 25}\right| + C \quad \longrightarrow \text{(II)}


Final matching:

(A) → (III)

(B) → (IV)

(C) → (I)

(D) → (II)

Therefore, the correct answer is Option 2.

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