Question

已知a+b=10,ab=20,求下列式子的值:

Answer 1

(1)a^2+b^2

=（a+b）^2-2ab

=10^2-2*20

=100-40

=60

(2)(a-b)^2

=（a+b）^2-4ab

=10^2-4*20

=100-80

=20