Question

很容易得分!若(a+b)^2=13,(a-b)^2=7,则a^2+b^2=_____,ab=_______.

Answer 1

a^2+b^2=[(a+b)^2+(a-b)^2]/2=(13+7)/2=10

ab=[(a+b)^2-(a-b)^2]/4=(13-7)/4=6/4=1.5