1)а²-а-6; 2)6а²+5а-4; 3)20х²-13ху+2у².

[latex]a^2-a-6\a_{1,2}=frac{1^+_-5}{2}\a_1=3 ;a_2=-2\a^2-a-6=(a-3)(a+2)\\6a^2+5a-4\a_{1,2}=frac{-5^+_-11}{12}\a_1=frac{1}{2} ;a_2=-frac{4}{3}\6a^2+5a-4=3*2(a-frac{1}{2})(a+frac{4}{3})=(2a-1)(3a+4)\\20x^2-13xy+2y^2=20x^2-5xy-8xy+2y^2=5x(4x-y)-2y(4x-\-y)=(5x-2y)(4x-y)[/latex]