Hello,

I start to solve this, but got stacked. Have no idea how to move on

Anybody help me ?

Code:5+8+11+…+ (3n+2) = 1/2n(3n+7) n=1 5+8+11+…+ (3*1+2) = 1/2 *1 (3*1+7) => 5=5 n=k 5+8+11+…+ (3k+2) = 1/2 k(3k+7) n=k+1 5+8+11+…+ (3(k+1)+2) = 1/2(k+1) (3(k+1)+7) 5+8+11+…+ (3k+5) = 1/2 (k+1) (3k+10) 5+8+11+…+ (3k+2) + (3k+5) = 1/2 (k+1) (3k+10) 1/2 k(3k+7) + (3k+5) = 1/2 (k+1) (3k+10) 1/2 [3k^2 + 10k + 5] = 1/2 (k+1) (3k+10) =>