1.7x^4-11x^2y^2-6y^4
=(7x^2+3y^2)(x^2-2y^2)
2.2(m+n) ^2+(m+n)-3
=[2(m+n)+3][(m+n)-1]
=(2m+2n+3)(m+n-1)
3.4(x-2y) ^2-8x+16y+3
=4(x-2y)^2-8(x-2y)+3
=[2(x-2y)-1][2(x-2y)-3]
=(2x-4y-1)(2x-4y-3)