1. ## subtracting polynomials

7x+1 - x^2+3x-8
i got x^2-4x+9 but my teacher said it was wronge. how do I correctly solve this problem?

2. Hello,

Where did the - go for x² ?

3. I am not sure why would the x^2 be negative i am so lost

I am not sure why would the x^2 be negative i am so lost
Are you subtracting the entire last 3 terms? If not, the original expression you entered was:

$\displaystyle 7x + 1 - x^2 + 3x - 8$

Grouping like terms and evaluating, we get:

$\displaystyle (7 + 3)x + (1 - 8) - x^2$
$\displaystyle 10x -7 - x^2$

Rearranging this into proper form, we get:
$\displaystyle -x^2 + 10x -7$

Does that make sense?

5. there where only 2 polnomials 7x+1 minus x^2+3x-8

there where only 2 polnomials 7x+1 minus x^2+3x-8
ok, then you should have written it like this:

$\displaystyle 7x + 1 - (x^2 + 3x - 8)$

Now, distribute the negative sign for the second polynomial:

$\displaystyle 7x + 1 - x^2 - 3x + 8$

Now group like terms:
$\displaystyle (7 - 3)x + (1 + 8) - x^2$
$\displaystyle -x^2 + 4x + 9$

7. thanks alot