39) a) 3x-6y
=3x-2.3y
=3(x-2y)
b) 2/5x2+5x3+x2y
=2/5.x.x+5.x.x2+x2y
=x(2/5x+5x2+x2y)
c) 14x2y-21xy2+28x2y2
=7.2x2y-7.3xy2+7.4x2y2
=7(2x2y-3xy2+4x2y2)
d)
2/5x(y-1)-2/5y(y-1)
=2/5(x-y)(y-1)
e)
10x(x-y)-8y(y-x)
=2.5x(x-y)+2.4y(x-y)
=2(5x-4y)(x+y)
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