Posted by **anonymous** on Saturday, May 25, 2013 at 10:07am.

1) (x^4+7x^3+7)-(2x^4-4x^3+1)

= -x^4+3x^3+6

2) (3n^3+n^2-n-4)+(5n^3-4n^2+11)

= 8n^3-3n^2-n+11

- polynomials am i doing it right? -
**MathMate**, Saturday, May 25, 2013 at 10:25am
You're on the right track...

1. expand it and write it out when it is a subtraction:

(x^4+7x^3+7)-(2x^4-4x^3+1)

= x^4+7x^3+7) -2x^4+4x^3-1

= -x^4 + *11* x^3 + 6

2. space out your terms to avoid losing some of them.

(3n^3 + n^2 -n -4)+(5n^3 -4n^2 + 11)

= 3n^3 + n^2 -n -4 + 5n^3 -4n^2 + 11

= 8n^3 - 3n^2 -n + 7

- polynomials am i doing it right? -
**anonymous**, Saturday, May 25, 2013 at 10:41am
for #1 i did

(x^4+7x^3+7)-(2x^4-4x^3+1)

= x^4+7x^3+7-2x^4-4x^3-1

= -x^4+3x^3+6

so why is it wrong?

- polynomials am i doing it right? -
**Mercy**, Saturday, May 25, 2013 at 10:45am
because you see that when you expanded the polynomials after the -2x^4 yu have a - instead of a positive because recall that when the brackets expand - and - = +.

That is the only thing you did wrong.

Good luck! you are on the right track though.

- polynomials am i doing it right? -
**anonymous**, Saturday, May 25, 2013 at 10:48am
ok thank you

- polynomials am i doing it right? -
**Mercy**, Saturday, May 25, 2013 at 10:52am
no problem:)

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