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?
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?
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:
$\displaystyle (7 - 3)x + (1 + 8) - x^2$
$\displaystyle -x^2 + 4x + 9$