someone tell me what i am doing wrong

Question

el_arrow · Answer

$$\int\limits_{-1}^{2} (x^3-2x)$$

el_arrow · Answer

i got -3/4 but the answer is positive

el_arrow · Answer

tell me what i am doing wrong

spyro517 · Answer

if its positive go with that

anonymous · Answer

We cannot tell you what you are doing wrong if you don't tell us what you did. The best we can do is tell you the correct way of doing it - but we can't tell you your mistake.

spyro517 · Answer

was the answer 3/4 or completely different?

anonymous · Answer

What did you do to get the answer of -3/4? We cannot guess your steps given the final answer you got.

anonymous · Answer

$$F(x)=\frac{x^4}{4}-x^2$$ compute 
$$F(2)-F(-1)$$

anonymous · Answer

Show us your work!

el_arrow · Answer

yeah but i want to know why its positive

anonymous · Answer

Here, let me give you hints. 

- Make sure you are substituting the 2 and substituting the 1 and then subtracting the result from 2 minus the result from -1. Not the other around.

anonymous · Answer

i can tell
you added, not subtracted

el_arrow · Answer

ok so i got 1/4x^-x^2

el_arrow · Answer

(1/4)x^(4)4-x^(2)

el_arrow · Answer

then i plug in the 2 and -1 for 2 i got 0

el_arrow · Answer

i am telling you my steps

el_arrow · Answer

and for -1 i got -3/4 but the answer in the back of my book says its positive 3/4

el_arrow · Answer

no i subtracted

anonymous · Answer

Yes, so the answer is 0 - (-3/4) = 3/4, as the book says. You take the upper bound and subtract the lower bound.