Question

Prove for any positive integer n, 1x2 + 2x3 + 3x4....n(n+1) = n(n+1)(n+2)/3

Answer 1

I’m kinda confused with your question but imma say 20

Answer 2

2)3+(+1)(+2)
(
k
)
(
k
+
1
)
(
k
+
2
)
3
+
(
k
+
1
)
(
k
+
2
)