Tips & Tricks TB Solution- Concept Used- Factorisation of a quadratic equation. Given Expression =x2−9x+20 Calculation- =x2−9x+20 =x2−5x−4x+20 =x(x−5)−4(x−5) =(x−4)(x−5) ∴ From the given options (x−4) is factor of x2−9x+20 Short trick- From the given options, we can put the different values of x in x2−9x+20 and check for which value x2−9x+20=0 Putting x=4 , we get x2−9x+20=0 ∴ x−4 is a factor of x2−9x+20.