If a1 = 1 and an+1= 2an + 5, n = 1, 2 .. , then a40 is equal to ?	Choose the most appropriate option:  A) a. 5*2^99-6  B) b. 5*2^99+6  C) c. 6*2^99+5  D) d. 6*2^39- 5  E) e. 6*2^99-6
Here is my 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= 2^2 *3 - 5................. so with same progression   a40= 2^40 * 3 - 5   a40=2 * 2^39 * 3 - 5   a40= 6 * 2^39 - 5   d. 6*2^39- 5
<result>D</result>
If a1 = 1 and an+1= 2an + 5, n = 1, 2 .. , then a40 is equal to ?