Răspuns:
Explicație pas cu pas:
N=49•1+49•3+...49•99 =
49 x ( 1 + 3 + ....+ 99) =
49 x (99 + 1) x 50 : 2 =
49 x 100 x 25 =
49 x 2500 =
7² x 50² =
(7 x 50)² =
350² = > patrat perfect
n = 49 x 1 + 49 x 3 + 49 x 5 + ......+ 49 x 999
= 49 x ( 1 + 3 + 5 + ........+ 999 )
= 49 x 500 x ( 1 + 999 ) / 2
= 49 x 500 x 1 000 / 2 =
= 49 x 500 x 500
= 7² x 500²
= (7 x 500)²
= (3500)² = > patrat perfect