subtraction question

[ginny1029]

Here is the original question
5x^3/2x^2+9x-5 - 4x^3-125/2x^2 +9x-5

here is what i did

5x^3-4x^3-125/2x^2+9x-5 = 1x^3-125/2x^2+9x-5

=(x-5)(x^2+5x+25)/(2x-1)(x+5)

the teacher gave us the answer as x^2-5x+25/2x-1
so I know I have my signs mixed up but I dont get WHY they are.

Thanks!!

 

[stapel]

Here is the original question
5x^3/2x^2+9x-5 - 4x^3-125/2x^2 +9x-5

here is what i did

5x^3-4x^3-125/2x^2+9x-5 = 1x^3-125/2x^2+9x-5

Assuming the second numerator to be 4x^3 - 125, the subtraction was -(4x^2 - 125), which simplifies as -4x^2 + 125. :wink:

 

[Loren]

Your teacher's answer is correct assuming you entered the problem incorrectly. To help us not have to be mind readers, please learn to use grouping symbols. Your entry of 5x^3/2x^2+9x-5 - 4x^3-125/2x^2 +9x-5 means
\(\displaystyle \frac{5x^3}{2x^2}+9x-5 - 4x^3-\frac{125}{2x^2} +9x-5\).
I think you meant 5x^3/(2x^2+9x-5) - (4x^3-125)/(2x^2 +9x-5). Please correct me if I'm wrong.