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

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

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?

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.

ok thank you

no problem:)

To simplify the first expression:

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

We can start by distributing the negative sign to each term inside the parenthesis:

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

Next, we can combine like terms by grouping the terms with the same exponent:

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

Simplifying each of these groups:

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

Therefore, the simplified form of the expression is -x^4 + 3x^3 + 6.

Now let's simplify the second expression:

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

Again, we'll start by distributing the addition sign to each term inside the parenthesis:

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

Next, we'll group the like terms with the same exponent:

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

Simplifying each of these groups:

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

Therefore, the simplified form of the expression is 8n^3 - 3n^2 - n + 7.

By following the steps of distributing and combining like terms, we can simplify algebraic expressions.