a.3x2-3xy-2x+2y =(3x2-3xy)-(2x-2y)
=3x.(x-y)-2.(x-y)
=(x-y).(3x-2)
b.6x2+3xy-2ax-ay =(6x2-2ax)+(3xy-ay)
=2x.(3x-a)+y.(3x-a)
=(3x-a).(2x+y)
c.x3-6x2+9x=x.(x2-6x+9)
=x.(x-3)2
d.2xy-x2-y2+25= -(-2xy+x2+y2-25)
= -[(x2-2xy+y2)-52)]
= -[(x-y)2-52 ]
= -(x-y+5).(x-y-5)
e.x2-y2-4yz-4z2= -(-x2+y2+4yz+4z2)
= -[(y2+4yz+4z2)-x2 ]
= -[ (y+2z)2-x2 ]
= -(y+2z+x).(y+2z-x)
f.2a2-4ab+2b2-8c2=2a2-2ab-2ab+2b2-4c2-4c2
=2.(a2-ab-ab+b2-2c2-2c2
=2.(a2-2ab+b2-4c2)
=2.[(a-b)2-(2c)2 ]
=2.(a-b+2c).(a-b-2c)
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