Skip to main contentSkip to solution

∫−11x3+∣x∣+1x2+2∣x∣+1dx\int_{-1}^1 \frac{x^3 + |x| + 1}{x^2 + 2|x| + 1}dx is equal to

Solution

✅ Correct Option: 2

The integral to evaluate is ∫−11x3+∣x∣+1x2+2∣x∣+1dx\int_{-1}^1 \frac{x^3 + |x| + 1}{x^2 + 2|x| + 1}dx

The integrand contains absolute values and the limits cross x=0x = 0.


The denominator can be simplified:

x2+2∣x∣+1=(∣x∣)2+2∣x∣+1x^2 + 2|x| + 1 = (|x|)^2 + 2|x| + 1

=(∣x∣+1)2= (|x| + 1)^2


Let f(x)=x3+∣x∣+1x2+2∣x∣+1f(x) = \frac{x^3 + |x| + 1}{x^2 + 2|x| + 1}

For x>0x > 0:

f(x)=x3+x+1(x+1)2f(x) = \frac{x^3 + x + 1}{(x+1)^2}

f(−x)=−x3+x+1(x+1)2f(-x) = \frac{-x^3 + x + 1}{(x+1)^2}

Adding these:

f(x)+f(−x)=(x3+x+1)+(−x3+x+1)(x+1)2f(x) + f(-x) = \frac{(x^3 + x + 1) + (-x^3 + x + 1)}{(x+1)^2}

=2x+2(x+1)2= \frac{2x + 2}{(x+1)^2}

=2(x+1)(x+1)2= \frac{2(x+1)}{(x+1)^2}

=2x+1= \frac{2}{x+1}


Using the symmetry property for integrals over [−a,a][-a, a]:

∫−11f(x)dx=∫01[f(x)+f(−x)]dx\int_{-1}^1 f(x)dx = \int_0^1 [f(x) + f(-x)]dx

Therefore:

∫−11x3+∣x∣+1x2+2∣x∣+1dx=∫012x+1dx\int_{-1}^1 \frac{x^3 + |x| + 1}{x^2 + 2|x| + 1}dx = \int_0^1 \frac{2}{x+1}dx


Evaluating the integral:

∫012x+1dx=2∫011x+1dx\int_0^1 \frac{2}{x+1}dx = 2\int_0^1 \frac{1}{x+1}dx

=2[ln⁡(x+1)]01= 2[\ln(x+1)]_0^1

=2[ln⁡(2)−ln⁡(1)]= 2[\ln(2) - \ln(1)]

=2ln⁡(2)= 2\ln(2)

=2log⁡e2= 2\log_e 2

Therefore, the answer is 2log⁡e22\log_e 2.

Keyboard Shortcuts

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