a+b=1
两边平方;
(a+b)^2=1*1
∴a^2+2ab+b^2=1
∴a^2+b^2=1-2ab=1+2*3=7
2a^3b+2ab^3=2ab(a^2+b^2)=2*(-3)*7=-42;
a+b=1,
两边*a
aa+ab=a;
a+b=1,
b=1-a代入ab=-3;
a=(1+√13)/6;或者a=(1-√13)/6
(a^2+ab)*(2a^3b+2ab^3)
=(-42)*a
=-42a
(a^2+ab)*(2a^3b+2ab^3)
=-42*(1+√13)/6
=-7-7√13;
或者(a^2+ab)*(2a^3b+2ab^3)
=-42*(1-√13)/6
=-7+7√13;
ab=-3
∴2a^3b+2ab^3