Q63 / 150 · MHT CET 2025 (21 Apr Shift 1) · Mathematics
$\int_2^4 \frac{\log x^2}{\log x^2+\log \left(36-12 x+x^2\right)} \mathrm{d} x$ is equal to
- Correct answerA$1$
- B$2$
- C$4$
- D$6$
Solution
Let $I = \int_2^4 \frac{\log x^2}{\log x^2 + \log(36-12x+x^2)}dx$.
Observe that $36 - 12x + x^2 = (6-x)^2$, so the integral becomes:
$I = \int_2^4 \frac{\log x^2}{\log x^2 + \log(6-x)^2}dx$
Using the substitution property $\int_a^b f(x)dx = \int_a^b f(a+b-x)dx$ with $a=2$, $b=4$:
$I = \int_2^4 \frac{\log(6-x)^2}{\log(6-x)^2 + \log x^2}dx$
Adding these two expressions for $I$:
$2I = \int_2^4 \frac{\log x^2 + \log(6-x)^2}{\log x^2 + \log(6-x)^2}dx = \int_2^4 1dx$
Evaluating the integral yields $2I = [x]_2^4 = 2$, hence $I = 1$.
Final answer: $\boxed{1}$
Hence, the correct answer is option: 'A'.