Question

plz help me to find answer ​of all these questions

Answer 1

a) Ans. 3

b) Ans. 2

c) Ans. 440

d) Proved in explanation part.

Step-by-step explanation:

Sum of n terms = n^2+2n

Sum of (n-1) terms = (n-1)^2+2(n-1)=n^2-1

nth term = Sum of n terms - Sum of (n-1) terms

= n^2+2n - (n^2-1)

= 2n+1

First term = 2×1+1 = 3

Second term = 2×2+1 = 5

Third term = 2×3+1= 7

Fourth term = 2×4+1 = 9

Common difference = 5-3=2

Sum of first 20 terms = 20/2(2×3+(20-1)×2)

= 440

Sum of n terms = n/2[2a+(n-1) d]

= n/2[2×3+(n-1)2]

=n^2+2n

Sum of n terms +1 = n^2+2n+1

= (n+1)^2