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Bikram Rawani

· started a discussion

· 1 Months ago

wahiyat (Question:327845.0)

ye set bekar hai isko hata dijiye ... sach me bekar hai..iske maths ke kuch questions aise hain jo illogical hain.

Question:

 If a1 = 1 and an + 1 = 2an + 5, n = 1, 2 ..., then a100 is equal to

Options:
A)

 [5 × 299 – 6]

B)

 [5 × 299 + 6]

C)

 [6 × 299 + 5]

D)

 [6 × 299 – 5]

Solution:

an+1=2an+5............(1)

lets ADD 5 to both sides....

so (an+1) + 5= 2 (an+5)....................taking 2 as common factor

now a1=1. so for n=1, an+5=6.......

putting n=1. we get both sides as,

a2 + 5= 2 * 6 ..............as (an+5=6 .......(for n=1))

a2= 2 *6 - 5

a2= 2 * 2 *3 - 5

a2= 22 *3 - 5................. so with same progression

a100= 2100 * 3 - 5

a100=2 * 299 * 3 - 5

a100= 6 * 299 – 5

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