y=3x^2-2x+1配方
问题描述：
y=3x^2-2x+1配方
答
y=3(x²-2x/3)+1
=3(x²-2x/3+1/9-1/9)+1
=3(x²-2x/3+1/9)-1/3+1
=3(x-1/3)²+2/3