Question 1040663
 (1 + 5x^2 -6x^3) and (14x^3 -7x^2 + 2) from  5x^3 +10x
The sum:
there are 6 terms
add or subtract like terms
1+2=3
5x^2-7x^2=-2x^2
-6x^3+14x^3=8x^3
There are no terms left out
we are subtracting 8x^3-2x^2+3 from 5x^3+10x

This is 
5x^3+0x^2+10x+0 MINUS
-(8x^3-2x^2+0x+3)
because the minus sign must be transmitted through the whole parentheses
5x^3+0x^2+10x+0
-8x^3+2x^2+0x-3), all the signs change, although it doesn't matter with 0x.
-3x^2+2x^2+10x-3


Like terms again
5x^3-8x^3=-3x^3
there is nothing to subtract -2x^2 from, so we have 0-(-2x^2)=2x^2
10x-0=10x
0-3=-3
All terms that are alike are worked with.  If a term is by itself, it must be kept, either unchanged if there is nothing to add or subtract or changed if there is.  Be careful and watch for signs.  Subtracting a negative makes it positive.
-3x^3+2x^2+10x-3