SOLUTION: x3+7x2-21x-27=0

Algebra ->  Equations -> SOLUTION: x3+7x2-21x-27=0      Log On


   

Question 331534: x3+7x2-21x-27=0
Found 2 solutions by JBarnum, Jk22:
Answer by JBarnum(2146) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E3%2B7x%5E2-21x-27=0
%28x%5E3-27%29%2B%287x%5E2-21x%29=0
%28x%5E3-3%5E3%29%2B7x%28x-3%29=0
hmm no solution that i can figure
i also tried this
http://www.algebrahelp.com/calculators/equation/calc.do?equation=x%5E3%2B7x%5E2-21x-27%3D0&solvf=AUTO
doesnt compute either

Answer by Jk22(389) About Me  (Show Source):
You can put this solution on YOUR website!
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