二次型f(x1,x2,x3)=x21+x22+x23+2x1x2+2x1x2+2x2x3的秩为____.

二次型f(x1,x2,x3)=x21+x22+x23+2x1x2+2x1x2+2x2x3的秩为____.
【正确答案】:1.