原式=(4x^2-2x+1/4)-9y^2 =(2x-1/2)^2-(3y)^2 =(2x-1/2+3y)(2x-1/2-3y)这是正确答案了
（4x)平方+1/4-(9x)平方-2x=16（x平方)+1/4-81(y平方）-2x
4x^2+1/4-9y^2-2x =(4x^2-2x+1/4)-9y^2 =(2x-1/2)^2-(3y)^2 =(2x-1/2+3y)(2x-1/2-3y)
