（1）(2x-y)(2x+y)-(x-3y)^2
=4x^2-y^2-(x^2-6xy+9y^2)
=4x^2-y^2-x^2+6xy-9y^2
=3x^2-10y^2+6xy
(2）(2a+b+1)(2a+b-1)
=((2a+b)+1)((2a+b)-1)
=(2a+b)^2-1
=4a^2+4ab+b^2-1
应该就是这样,ok了