If x=p, x=q, and x=r are three roots of cubic equation x3+bx2+cx+d=0, then we understand that cubic factors in form x3+bx2+cx+d=(x-p)(x-q)(x-r). Using this knowledge, illustrate how coefficients a,b,c, and d can be written in terms of p,q, and r. Show results by discussing roots of equation x3-2x2-2x+1=0.