Question 331534
P(x)=x3+7x2-21x-27=0

Check : P(-1)=-1+7+21-27=0, hence P(x) is dividable by x+1 : 

x^3+7x^2-21x-27 | x+1
---------------------
x^3+x^2_________| x^2+6x-27
----------------|----------
6x^2-21x________|
6x^2+6x_________|
--------------------------
-27x-27_________|
-27x-27
---------------------------
0

=>P(x)=(x+1)(x^2+6x-27)=(x+1)(x+9)(x-3) by Viete's method