NIMCET 2014 — Mathematics PYQ
NIMCET | Mathematics | 2014The value of ∫xexdx is equal to:
Choose the correct answer:
- A.
2x−ex−4xex+C
(2x−4x+4)ex+C
Explanation
Solution
Concept:
-
Integration by Parts: ∫f(x)g(x)dx=f(x)∫g(x)dx−∫[f′(x)∫g(x)dx]dx
-
Integration by substitution: If we substitute x=f(t), then dx=f′(t)dt and ∫f(x)dx=∫f[f(t)]f′(t)dt
-
∫exdx=ex+C
Calculation:
Let I=∫xexdx
Substituting x=t, we get:
Integrating by parts, taking t2 as the first function and et as the second function, we get:
Integrating ∫tetdt by parts, we get:
Back substituting x=t, we get:
Correct Option: 2. (2x−4x+4)ex+C
Explanation
Solution
Concept:
-
Integration by Parts: ∫f(x)g(x)dx=f(x)∫g(x)dx−∫[f′(x)∫g(x)dx]dx
-
Integration by substitution: If we substitute x=f(t), then dx=f′(t)dt and ∫f(x)dx=∫f[f(t)]f′(t)dt
-
∫exdx=ex+C
Calculation:
Let I=∫xexdx
Substituting x=t, we get:
Integrating by parts, taking t2 as the first function and et as the second function, we get:
Integrating ∫tetdt by parts, we get:
Back substituting x=t, we get:
Correct Option: 2. (2x−4x+4)ex+C

