a^3b+2a^2b^2+ab^3=ab(a²+2ab+b²)=ab(a+b)²=3×5²=75
a^3b+2a^2b^2+ab^3=ab(a^2+2ab+b^2)=ab(a+b)^2=3X5^2=3X25=75
用matlab解
