Subtracting 3x2 + 4x – 5 from 7x2 + x + 9 results in a polynomial. after subtracting 4x2 – 3x from this polynomial, the difference is . nextreset

Writing it out in a string of expressions you get this:
7x^2 + x + 9 - (3x^2 + 4x - 5). Now don't forget that that negative sign out in front of the second polynomial changes the signs inside that set of parenthesis. so it would actually be 7x^2+x+9-3x^2-4x+5.  Now let's simplify. 4x^2-3x+14 is that answer.  Now to do the rest of the subraction...4x^2-3x+14-(4x^2-3x).  Again, the negative sign is going to change the signs inside the parenthesis giving us 4x^2-3x+14-4x^2+3x.  The 4x^2 terms cancel out as do the 3x terms, leaving us only with the 14.

If you make it a little more clear i can answer it