1、(2x+3y)^2-(3x-2y)^2
=(2x+3y+3x-2y)(2x+3y-3x+2y)
=(5x+y)(5y-x)
2、49a^4b^2-64c^2(x+2y)2
=(7a^2b) ^2-[8c(x+2y)]^2
=[7a^2b+8c(x+2y)][7a^2b-8c(x+2y)]
=(7a^2b+8cx+16cy)(7a^2b-8cx-16cy)
3、(2x-y)^2-(x+2y)^2
=(2x-y+x+2y)(2x-y-x-2y)
=(3x+y)(x-3y)