For the answer to the question above, 
(3•(x2))+2x)+(7•(x3)))+(((2•5x2)+6x)+9)
(3•(x2))+2x)+7x3)+(10x2+6x+9)
 ((3x2 + 2x) + 7x3) + (10x2 + 6x + 9)
7x3+13x2+8x+9  is not a perfect cube.
split the expression at hand into groups, each group having two terms 
Group 1:  8x+9 
Group 2:  7x3+13x2 
then pull out from each group separately.
Group 1:   (8x+9) • (1)
Group 2:   (7x+13) • (x2)
Find roots (zeroes) of :       F(x) = 7x3+13x2+8x+9
Polynomial Roots Calculator is a set of methods aimed at finding values of x  for which   F(x)=0  
to make this short, 
In this case, the Leading Coefficient is  7  and the Trailing Constant is  9. 
The factors of the Leading Coefficient:  1,7 
the factors of the Trailing Constant:  1,3 ,9 
So the answer is 7x3 + 13x2 + 8x + 9