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?

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- Mar 25th 2008, 10:47 AMimbadatmathsubtracting 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? - Mar 25th 2008, 11:06 AMMoo
Hello,

Where did the - go for x² ? - Mar 25th 2008, 11:28 AMimbadatmath
I am not sure why would the x^2 be negative i am so lost

- Mar 25th 2008, 11:41 AMmathceleb
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? - Mar 25th 2008, 11:45 AMimbadatmath
there where only 2 polnomials 7x+1 minus x^2+3x-8

- Mar 25th 2008, 11:47 AMmathceleb
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:

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

$\displaystyle -x^2 + 4x + 9$ - Mar 25th 2008, 12:05 PMimbadatmath
thanks alot