NIMCET 2017 — Mathematics PYQ
NIMCET | Mathematics | 2017If (1−x+x2)n=a0+a1x+a2x2+⋯+a2nx2n, then a0+a2+a4+⋯+a2n is?
Choose the correct answer:
- A.
23n+1
(Correct Answer) - B.
23n−1
23n+1
Explanation
Calculation:
Given,
(1−x+x2)n=a0+a1x+a2x2+⋯+a2nx2n
Put, x=1,
(1−1+12)n=a0+a1+a2+⋯+a2n
⇒1=a0+a1+a2+⋯+a2n ......(1)
Put, x=−1,
(1+1+(−1)2)n=a0−a1+a2−a3+⋯+a2n
⇒3n=a0−a1+a2−a3+⋯+a2n ......(2)
Adding (1) and (2),
2(a0+a2+a4+⋯+a2n)=3n+1
⇒a0+a2+a4+⋯+a2n=23n+1
Hence, option (1) is correct.
Explanation
Calculation:
Given,
(1−x+x2)n=a0+a1x+a2x2+⋯+a2nx2n
Put, x=1,
(1−1+12)n=a0+a1+a2+⋯+a2n
⇒1=a0+a1+a2+⋯+a2n ......(1)
Put, x=−1,
(1+1+(−1)2)n=a0−a1+a2−a3+⋯+a2n
⇒3n=a0−a1+a2−a3+⋯+a2n ......(2)
Adding (1) and (2),
2(a0+a2+a4+⋯+a2n)=3n+1
⇒a0+a2+a4+⋯+a2n=23n+1
Hence, option (1) is correct.

