a) 9y²-(x²-8x+16)=9y²-(x-4)²=(3y-x+4)(3y+x-4)
c) 36x²+12x+1-49y² =(6x+1)²-49y² =(6x+1-7y)(6x+1+7y)
d) x²-12x+36-y²-8y-16=(x-6)²-(y+4)²=(x-6-y-4)(x-6+y+4)=(x-y-10)(x+y-2)
e) x²+14xy +49y²-a²-6ab-9b²= (x+7y)²-(a+3b)²=(x+7y-a-3b)(x+7y+a+3b)
f)(9x²-6x+1)-(4x²+12x+9)=(3x-1)²-(2x+3)²=(3x-1-2x-3)(3x-1+2x+3)=(x-4)(5x+2)
g)(16x²+8x+1)-(9x²-12x+4)=(4x+1)²-(3x-2)²=(4x+1-3x+2)(4x+1+3x-2)=
=(x+3)(7x-1)