How in the world did you get a quadratic equation out of this? [itex]y(2)= (C_1+ 6C_2)e^6= e^6[/itex] and [itex]y'(1)= (3C_1+ 4C_2)e^3= e^3[/itex]. The derivative is [itex]y'= 3C_1e^{3x}+ C_2e^{3x}+ 3C_2xe^{3x}= ([3C_1+ C_2]+ 3C_2x)e^x[/itex]. It does not involve "[itex]C_1C_2[/itex]"!
You have [itex]C_1+ 6C_2= 1[/itex] and [itex]3C_1+ 4C_2= 1[/itex], two linear equations.