(i) The greatest common factor of the terms namely, 3x and 15 of the expression 3x + 15 is 3. Also, 3x=3×x and 15=3×5
∴3x+15=3(x+5)
(ii)2x2=2x×x and 5x=5×x
∴2x2+5x=2x×x+5×x=(2x+5)x
(iii) Clearly, 3xy is the greatest common factor of the terms 3x2y and 6xy2 of the binomial 3x2y–6xy2.
Also, 3x2y=3xy×x and 6xy2=3xy×2y
∴3x2y–6xy2=3xy×x–3xy×2y=3xy(x–2y)