已知a^2+b^2=11,ab=3,则a+b

问题描述:

已知a^2+b^2=11,ab=3,则a+b

答:
a^2+b^2=11
ab=3
(a+b)^2=a^2+2ab+b^2
=11+2*3
=11+6
=17
a+b=±√17