Răspuns:
Explicație pas cu pas:
2k-1 ; 2k+1 ; 2k+3 ; 2k+5
(2k+5)³ - (2k-1)(2k+1) +2k+3 = numar impar ?
(2k+5)(4k²+20k+25) - 4k²+1 + 2k+3 =
= 8k³+40k²+50k+20k²+100k+125-4k²+2k+4 =
= 8k³+56k²+152k+129 = numar impar
8k³ = numar par ; 56k² = numar par ;
152k = numar par ; 129 = numar impar .
