Question

1.1/4+a^2+a^42.(1/36a-1/3)a+13.(x^2-2xy+y^2)+(-2x+2y)+1

Answer 1

1.(a^2+1/2)^2

2.(1/36a-1/3)a+1 =(1/6*a-1)^2

3.(x^2-2xy+y^2)+(-2x+2y)+1

=(x-y)^2-2(x-y)+1

=(x-y-1)^2

看懂了吗?