Skip to main contentSkip to solution

Match List-I with List-II

List-IList-II
Definite integralValue
------
(A) ∫1elog⁡xxdx\int_{1}^{e} \frac{\log x}{x} dx(I) 4
(B) ∫−22x3(1−x2)dx\int_{-2}^{2} x^3(1 - x^2) dx(II) 12\frac{1}{2}
(C) ∫12x dx\int_{1}^{2} x \, dx(III) 0
(D) ∫−22∣x∣dx\int_{-2}^{2} \vert x\vert dx(IV) 32\frac{3}{2}

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

∫1elog⁡xx dx\int_{1}^{e} \frac{\log x}{x}\, dx

Let t=log⁡x  ⟹  dt=1x dxt = \log x \implies dt = \frac{1}{x}\,dx

When x=1x = 1, t=0t = 0 and when x=ex = e, t=1t = 1

∫01t dt=[t22]01\int_{0}^{1} t\, dt = \left[\frac{t^2}{2}\right]_0^1

=12−0= \frac{1}{2} - 0

=12= \frac{1}{2}

(A) → (II)


∫−22x3(1−x2) dx\int_{-2}^{2} x^3(1 - x^2)\, dx

Let f(x)=x3(1−x2)=x3−x5f(x) = x^3(1 - x^2) = x^3 - x^5

f(−x)=(−x)3−(−x)5=−x3+x5=−f(x)f(-x) = (-x)^3 - (-x)^5 = -x^3 + x^5 = -f(x)

Since f(x)f(x) is an odd function, ∫−aaf(x) dx=0\int_{-a}^{a} f(x)\,dx = 0

∫−22x3(1−x2) dx=0\int_{-2}^{2} x^3(1 - x^2)\, dx = 0

(B) → (III)


∫12x dx\int_{1}^{2} x\, dx

=[x22]12= \left[\frac{x^2}{2}\right]_1^2

=42−12= \frac{4}{2} - \frac{1}{2}

=32= \frac{3}{2}

(C) → (IV)


∫−22∣x∣ dx\int_{-2}^{2} |x|\, dx

Since ∣x∣|x| is an even function, ∫−aaf(x) dx=2∫0af(x) dx\int_{-a}^{a} f(x)\,dx = 2\int_{0}^{a} f(x)\,dx

=2∫02x dx= 2\int_{0}^{2} x\, dx

=2[x22]02= 2\left[\frac{x^2}{2}\right]_0^2

=2(42−0)= 2\left(\frac{4}{2} - 0\right)

=4= 4

(D) → (I)


List-IList-II
(A)(II) 12\frac{1}{2}
(B)(III) 00
(C)(IV) 32\frac{3}{2}
(D)(I) 44

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question