c) primele 10 nr nat pare: 2,4,6,8,10,12,14,16,18,20
primele 10 nr nat ≠ 0: 1,2,3,4,5,6,7,8,9,10
2+4+6+...+20=2(1+2+3+...+10)=2[(10×11):2]=2×55=110
1+2+3+...+10=(10×11):2=110:2=55
110:55=2
d) 24²+2×13+7=576+26+7=609
3⁴+1-5=81+1-15=67
609:67=9.0895522388 (ori am gresit eu ori este gresit exeecitiul)
