The user wants me to solve the definite integral:
I=0∫11+x2x4(1−x)4dx
This is a well-known integral related to an approximation of π. Let's solve it from first principles.
Step 1: Expand the numerator.
The numerator is N(x)=x4(1−x)4=(x(1−x))4=(x−x2)4.
Using the binomial expansion for (a−b)4=a4−4a3b+6a2b2−4ab3+b4.
Here, a=x and b=x2.
So, N(x)=(x)4−4(x)3(x2)+6(x)2(x2)2−4(x)(x2)3+(x2)4
N(x)=x4−4x5+6x6−4x7+x8.
So the integral becomes:
I=∫011+x2x8−4x7+6x6−4x5+x4dx
Step 2: Perform polynomial long division.
We need to divide the numerator polynomial P(x)=x8−4x7+6x6−4x5+x4 by the denominator polynomial D(x)=x2+1.
Performing the long division:
So, the division gives a quotient Q(x)=x6−4x5+5x4−4x2+4 and a remainder R(x)=−4.
Therefore, the integrand can be written as:
1+x2x8−4x7+6x6−4x5+x4=(x6−4x5+5x4−4x2+4)−1+x24
Step 3: Integrate the resulting expression.
The integral now is:
I=∫01(x6−4x5+5x4−4x2+4−1+x24)dx
Let's integrate term by term:
I=[7x7−46x6+55x5−43x3+4x−4tan−1(x)]01
I=[7x7−32x6+x5−34x3+4x−4tan−1(x)]01
Step 4: Evaluate the definite integral.
Now, substitute the limits of integration.
The value at the lower limit x=0 is 0 for all terms.
So, we just need to evaluate at the upper limit x=1.
I=(717−32(1)6+15−34(1)3+4(1)−4tan−1(1))−(0)
I=71−32+1−34+4−4(4π)
I=71−(32+34)+(1+4)−π
I=71−36+5−π
I=71−2+5−π
I=71+3−π
Now, combine the fractions:
I=71+3×7−π
I=71+21−π
I=722−π
Step 5: Compare with the options.
The calculated value is I=722−π.
Let's check the given options:
A: 722−π
B: 1052
C: 0
D: 1571−23π
Our result matches option A exactly.