JEE 2022 — Mathematics PYQ
JEE | Mathematics | 2022The value of limx→1x4−2x3+2x−1(x2−1)sin2(πx) is equal to:
Choose the correct answer:
- A.
6π2
- B.
3π2
π2
Explanation
Solution (for x→1)
-
Factorize Denominator: x4−2x3+2x−1=(x2−1)(x2+1)−2x(x2−1)=(x2−1)(x2−2x+1)=(x2−1)(x−1)2.
-
Simplify the limit expression:
x→1lim(x2−1)(x−1)2(x2−1)sin2(πx)=x→1lim(x−1)2sin2(πx) -
Substitution: Let h=x−1. As x→1,h→0.
h→0limh2sin2(π(1+h))=h→0limh2(−sin(πh))2=h→0limh2sin2(πh) -
Standard Limit: limh→0(πhsin(πh))2⋅π2=1⋅π2=π2.
Correct Option: (D) π2
Explanation
Solution (for x→1)
-
Factorize Denominator: x4−2x3+2x−1=(x2−1)(x2+1)−2x(x2−1)=(x2−1)(x2−2x+1)=(x2−1)(x−1)2.
-
Simplify the limit expression:
x→1lim(x2−1)(x−1)2(x2−1)sin2(πx)=x→1lim(x−1)2sin2(πx) -
Substitution: Let h=x−1. As x→1,h→0.
h→0limh2sin2(π(1+h))=h→0limh2(−sin(πh))2=h→0limh2sin2(πh) -
Standard Limit: limh→0(πhsin(πh))2⋅π2=1⋅π2=π2.
Correct Option: (D) π2

