=x^2+(4+5)x+20
= x^2+4x+5x+20
=x(x+4) +5(x+4)
=(x+4) (x+5)
Follow rule:-
- Here we first multiple constant term 20 and cofficient of x^2 , means 20×1=20
- Again do prime factorisation of 20,means=2×2×5
- Again, For example 20 sign +ve means middle term is completed by add
- So, (4+5)x
