a) 73x538-73x500-73x37=73(538-500-37)=73*1=73
c)299(300*298-2*198)=299*(89400-396)=299*89004=26612196
b) 3+6+9+...+90=3(1+2+3+.......+30)=3*(30*31:2)=3*465=1395
am folosit suma lui Gauss adica: 1 + 2 + 3 + 4 + … + n = n x ( n + 1 ) : 2 unde n este numarul de termeni