Răspuns:
Explicație pas cu pas:
18.
1 + 3 + 5 + .....+ 99 = 50 × ( 1+99):2 = 50 × 100:2= 50 x 50 = 50² -> patrat perfect
( 99 - 1 ) : 2 + 1 = 98 : 2 + 1 = 49 + 1 = 50 termeni are suma
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17.
2 + 4 + 6 + ..... + 100 =
= 2 × ( 1 + 2 + 3 + ..... + 50 ) =
= 2 × 50 × ( 1 + 50 ) : 2 =
= 50 × 51 → nu e patrat perfect
= 5² × 2 × 3 × 17
