Find the remainder when f(x) = 2x^3 – 12x^2 + 11x + 2 is divided by x – 5.
is the answer 7? I'm not sure?

Question

Find the remainder when f(x) = 2x^3 – 12x^2 + 11x + 2 is divided by x – 5.
is the answer 7? I'm not sure?

lgbasallote · Answer

according to wolframalpha it's not

lgbasallote · Answer

you may have done something wrong in your division

anonymous · Answer

okay. I dnt know where I went wrong then...

anonymous · Answer

did u use synthetic division??? i would

lgbasallote · Answer

or i inputted something wrong in wolfram

lgbasallote · Answer

im gonna do this by hand now..

anonymous · Answer

No I didn't use that method.

anonymous · Answer

–3 

 3 

 –7

anonymous · Answer

its all ways eaiser

anonymous · Answer

these are the rest of the answers.

anonymous · Answer

what did you get on wolfalpha?

lgbasallote · Answer

wait..this software is so choosy lol

anonymous · Answer

i got -7

lgbasallote · Answer

lol i hate this software

lgbasallote · Answer

yeah i think it's -7

anonymous · Answer

okay lol. and thank you katie.

anonymous · Answer

ur welcome!!

lgbasallote · Answer

moral: dont trust a software haha

anonymous · Answer

and yah it really is choosy so that's why I dnt use it.

anonymous · Answer

ikr :)

anonymous · Answer

yeah i prefer free hand lol

anonymous · Answer

I'll try that one next time lol well thanks guys.

anonymous · Answer

$$f(x) = 2x^3 – 12x^2 + 11x + 2 $$$$f(5) = 2\times 5^3 – 12x\times 5^2 + 11\times5  + 2 $$ is your remainder

anonymous · Answer

are you sure?

anonymous · Answer

$$f(5) = 2\times 5^3 – 12\times 5^2 + 11\times5  + 2$$ typo there

lgbasallote · Answer

@satellite73 remind me again how to use remainder theorem?

anonymous · Answer

very sure

anonymous · Answer

if you divide a polynomial $p(x)$ by $x-k$ your remainder is $p(k)$

anonymous · Answer

that's not any of my choices tho, so Idk.

anonymous · Answer

did you compute?

anonymous · Answer

no, I re did it by hand.

anonymous · Answer

and I got  -7 like they said.

anonymous · Answer

i get 7

anonymous · Answer

lets cheat shall we? http://www.wolframalpha.com/input/?i=%282x^3+%E2%80%93+12x^2+%2B+11x+%2B+2%29%2F%28x-5%29

lgbasallote · Answer

yup i got 7 too using remainder theorem

lgbasallote · Answer

how'd you make wolframalpha work o.O

anonymous · Answer

ahhhh sorry

anonymous · Answer

i used the rong sign

lgbasallote · Answer

oh lol i made a syntax error in wolfram a while ago no wonder

anonymous · Answer

$$f(x)=2 x^3-12 x^2+11 x+2 = (1-2 x+2 x^2)×(x-5)+7$$ and so it is pretty clear that $f(5)=7$ because the second factor will be 0 leaving 7 as the answer