5-4x-x^2=
d=4^2-4*5*(-1)=36
x1=(4+sqrt36)/2=5
x2=(4-sqrt36)/2=-1
(x-5)(x+1)
x^2-2*x-3
D=2^2-1*(-3)*4=16
x1=(2+4)/2=3
x2=(-2+4)/2=-1
(x+1)(x-3)
sqrt(x-5)(x-3)(x+1)^2=x+1sqrt(x-5)(x-3)
