已知(a+b)^2=11,ab=2,则(a-b)^2=
问题描述:
已知(a+b)^2=11,ab=2,则(a-b)^2=
答
(a+b)^2=11,a^2+2ab+b^2=11 ab=2,a^2+4+b^2=11
a^2+4+b^2=7
(a-b)^2= a^2-2ab+b^2=7-4=3