Question 22166
I do these different than most people. You are multiplying these numbers together, so use x+2 and multiply the x by each number/variable in the second equation then multiply the 2 by each number/variable in the second equation. then do the adding and subtraction of the common factors.

like I said I do it different, I do it like long multiplication, it makes it easier for me and I will show you how...maybe it will help... 

 x^2-3x+8                             multiply just like you would
*     x+2                             with all numbers in the equation
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      2x^2-6x+16                       make sure you line up with the
 x^3 -3x^2+8x                          same type of number or variable
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  x^3-x^2+2x+16
you can do this problem in the other form that is usually taught,
(x+2)(x^2-3x+8)   
take the x and multiply each number in the second equation by x  
 x*x^2 is x^3   x*(-3x)=-3x^2   x*8=8x  
by 2    
 x^2*2=2x^2     2*(-3x)=-6x     x*8=16
so you have x^3-3x^2-8x+2x^2-6x+16
combine the common factors and you have x^3-3x^2+2x^2-6x+8x+16=
x^3-x^2+2x+16