上装式球阀型号:a+b=3,ab=-1
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a^2b+ab^2=
(a-b)^2=
a^2+b^2=
(a-b)^2=
a^2+b^2=
a^2b+ab^2
=ab(a+b)
=(-1)(3)
=-3
(a-b)^2
=a^2+b^2-2ab
=a^2+b^2+2ab-4ab
=(a+b)^2-4ab
=3^2-4(-1)
=13
a^2+b^2
=(a+b)^2-2ab
=3^2-2(-1)
=11
a^2b+2b^2
=a(ab)+b(ab)
=ab(a+b)
代入=-1*3=-3
(a-b)^2
=(a+b)^2-4ab
代入=3^2-4*(-1)=9+4=13
a^2+b^2=(a+b)^2-2ab
代入=3^2+2=9+2=11