1! + 2*2! + 3*3! + ... + n*n! = (n+1)! - 1�
by induction :�
for n = 1, 1! = 1 and (1+1)! - 1 = 2 - 1 = 1 : it's true�
supposing it's true for n, we proove it's true for n+1 :�
1! + 2*2! + ... + n*n! + (n+1)*(n+1)! = (n+1)! - 1 + (n+1)*(n+1)!�
= (n+1)! (1 + n+1) - 1�
= (n+2)(n+1)! - 1�
=(n+2)! - 1�
it's true for n+1, then it's true for all n�1! + 2*2! + 3*3! + ... + n*n! = (n+1)! - 1�
by induction :�
for n = 1, 1! = 1 and (1+1)! - 1 = 2 - 1 = 1 : it's true�
supposing it's true for n, we proove it's true for n+1 :�
1! + 2*2! + ... + n*n! + (n+1)*(n+1)! = (n+1)! - 1 + (n+1)*(n+1)!�
= (n+1)! (1 + n+1) - 1�
= (n+2)(n+1)! - 1�
=(n+2)! - 1�
it's true for n+1, then it's true for all n�1! + 2*2! + 3*3! + ... + n*n! = (n+1)! - 1�
by induction :�
for n = 1, 1! = 1 and (1+1)! - 1 = 2 - 1 = 1 : it's true�
supposing it's true for n, we proove it's true for n+1 :�
1! + 2*2! + ... + n*n! + (n+1)*(n+1)! = (n+1)! - 1 + (n+1)*(n+1)!�
= (n+1)! (1 + n+1) - 1�
= (n+2)(n+1)! - 1�
=(n+2)! - 1�
it's true for n+1, then it's true for all n�