a³+b³=a³+a²b-a²b+b³=a²(a+b)-b(a²-b²)=a²(a+b)-b(a+b)(a-b)=(a+b)(a²-ab+b²)a^(3/2) + b^(3/2) = [a^(1/2) + b ^(1/2)][a- (ab)^(1/2) + b]