Question

Poate cineva sa continuie ?

Answer 1

k ( 2 k - 1 ) ( 2 k + 1 ) / 3  +  3 ( 2 k + 1 )² / 3 =

= k ( 4 k² - 1 ) / 3 + 3 ( 4 k ² + 4 k + 1 ) / 3 =

=  ( 4 k³ - k )  / 3 + ( 12 k² + 12 k + 3 ) / 3 =

= ( 4 k³ + 12 k ² + 11 k + 3 ) / 3

sau dai factor comun pe 2 k + 1

= ( 2 k + 1 ) (  2 k² - k + 6 k + 3 )   / 3 =

= ( 2 k + 1 ) ( 2 k² + 5 k + 3 ) / 3