先把他乘以4会比较好运算
(4(x+1)(x+2)+1)/4 (要记得除以4,因为题目并没有真的放大4倍)
=(4x^2+12x+8+1)/4
=(4x^2+12x+9)/4
=x^2+3x+2.25
=(x+1.5)^2