Given: ∫ex((x+1)3x−1)dx=(x+1)BAex+C
For integrals involving ex, the formula is:
∫ex[f(x)+f′(x)]dx=ex⋅f(x)+C
From the answer form (x+1)BAex, let:
f(x)=(x+1)BA
Finding f′(x):
f′(x)=A⋅(−B)⋅(x+1)−B−1
f′(x)=(x+1)B+1−AB
Calculate f(x)+f′(x):
f(x)+f′(x)=(x+1)BA+(x+1)B+1−AB
=(x+1)B+1A(x+1)−AB
=(x+1)B+1A(x+1−B)
Matching with the given expression:
(x+1)B+1A(x+1−B)=(x+1)3x−1
Comparing denominators:
B+1=3
B=2
Comparing numerators:
A(x+1−B)=x−1
Substituting B=2:
A(x−1)=x−1
A=1
Therefore:
(B) A=1 is correct
(D) B=2 is correct
The correct answer is: (B) and (D) only