[" 5.The values of "n," if "50+46+42+38+......" to n terms "=336" is "],[[" a) "12,14," b) "10,16," c) "8,18," d) "6,20]]

2+ 3.2 + 4.2^(2) + …... upto n terms =

Find the value of n if ^nP_5=42^nP_3,n>4

S_(n)=54+51+48+......n terms =513 Value of n is

Find the value of n such that : "^nP_5=42 ^nP_3, n>4 .

The value of n for which the n^(th) terms of the A.P.s 2,10,18,"…"and 38,40,42,"…" are equal ,

2.5+3.8+4.11+.....+ upto n terms =n(n^(2)+4n+5), n in N

Find the values of n and r if ""^nP_r=336,""^nC_r=56 .

336,168,84,42,21,?

Find the sum of the following arithmetic progressions: (i) 50 ,\ 46 ,\ 42 ,\ ... to 10 terms (ii) 1,\ 3,\ 5,\ 7,\ ... to 12 terms (iii) 3,\ 9//2,\ 6,\ 15//2,\ ... to 25 terms