Question

1.已知（a+b)的平方=17,ab=3,求a的平方+b的平方与(a-b)的平方的值.

Answer 1

(a+b)^2=a^2+2ab+b^2
a^2+b^2
=a^2+2ab+b^2-2ab
=17-6=11
(a-b)=a^2+2ab+b^2-4ab--------------------(a-b)^2=a^2-2ab+b^2
=17-12=5
a^2+b^2=11 (a-b)^2=5