Question

已知a-b=5,ab=3,求(a+b)^2与a^2+b^2的值

Answer 1

a-b=5,ab=3

则有(A-B)^2=A^2-2AB+B^2=25

==>A^2+B^2=25+2AB=31

所有(A+B)^2=A^2+B^2+2AB=31+2*3=37

A^2+B^2=31