\(a,3x^2-6x=3x.\left(x-2\right)\\ b,x^2+4x-25y^2+4=\left(x^2+4x+4\right)-25y^2\\ =\left(x+2\right)^2-\left(5y\right)^2\\ =\left(x-5y+2\right).\left(x+5y+2\right)\\ c,2x^2-5x-3\\ =2x^2-6x+x-3\\ =2x.\left(x-3\right)+\left(x-3\right)\\ =\left(2x+1\right).\left(x-3\right)\)
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a, = 3x ( x - 2 )
b, = ( x2 + 4x + 4 ) - 25y2
= ( x + 2 )2 - 25y2
= ( x + 2 - 5y ) ( x + 2 + 5y )
c, 2x2 - 5x + 3
= 2x2 - 6x + x + 3
= 2x ( x - 3 ) + ( x - 3 )
= ( x - 3 ) ( 2x + 1 )
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c) 2x2(x +1) + 4x(x +1); d) 2 x(y - 1) - 2