Let be a sequence such that a0 = a1 = 0 and an+2 = 3an+1 – 2an + 1, . Then is equal to
Let be a sequence such that a0 = a1 = 0 and an+2 = 3an+1 – 2an + 1, . Then is equal to
Option 1 -
483
Option 2 -
528
Option 3 -
575
Option 4 -
624
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1 Answer
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Correct Option - 2
Detailed Solution:a0 = 0, a1 = 0
an+2 = 3an+1 – 2an + 1
a25 a23 – 2a25a22 – a23a24 + 4a22a24 =?
a2 = 3a1 – 2a0 + 1
a3 = 3a2 – 2a1 + 1
a4 = 3a3 – 2a2 + 1
a5 = 3a4 – 2a3 + 1
an+2 = 3an+1 – 2an + 1
⇒ an+2 = 2 (a2 + a3 + …. + an + an+1) –2 (a1 + a2 + ….+ an) + n + 1
an+2 = 2an+1 + n + 1
a25 a23 -2a25 a22 -a23 a24 + 4a22 a24
= a25 (a23 – 2a22) -2a24 (a23 – 2a22)
As an+2 = 2an+1 + n + 1
⇒ an+2 – 2an+1 = n + 1
⇒ an+1 -2an = n
⇒ 24 × 22 = 528
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