已知x^2+2/3x+1可以通过配方变形为(x+m)^2+n,则mn=
问题描述：
已知x^2+2/3x+1可以通过配方变形为(x+m)^2+n,则mn=
答
x² + 2/3 x +1
= [ x² + 2*x*1/3 + (1/3)² ] - (1/3)² +1
= (x +1/3)² + 8/9
m=1/3,n=8/9
mn= 8/27