# Algebra, is it possible to..

**URL:** <https://boards.straightdope.com/t/algebra-is-it-possible-to/81241>\
**Category:** Factual Questions\
**Created:** [September 13, 2001, 2:37am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241 "2001-09-13T02:37:45Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Sterra](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@Sterra](https://boards.straightdope.com/u/Sterra)\
**Post date:** [September 13, 2001, 2:37am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/1 "2001-09-13T02:37:45Z")

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solve an equation that is x+x^2=800? I am doing a problem and I can’t get it further than that.

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**Author:** ![The\_Peyote\_Coyote](https://avatars.discourse-cdn.com/v4/letter/t/5f8ce5/32.png) [@The\_Peyote\_Coyote](https://boards.straightdope.com/u/The_Peyote_Coyote)\
**Post date:** [September 13, 2001, 2:40am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/2 "2001-09-13T02:40:00Z")

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Try subtracting 800 from both sides of the equation and applying the quadratic formula.

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**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\
**Post date:** [September 13, 2001, 2:50am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/3 "2001-09-13T02:50:26Z")

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> [@](#):
>
> \*Originally posted by Sterra \*  
> \*\*solve an equation that is x+x^2=800? I am doing a problem and I can’t get it further than that. \*\*

Start by re-arranging it as x[sup]2[/sup] + x - 800 = 0.

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**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\
**Post date:** [September 13, 2001, 2:52am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/4 "2001-09-13T02:52:57Z")

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Yeah, what **The Peyote Coyote** and **Anthracite** said. The quadratic formula is easy to find on Google, just in case you don’t have it present.

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**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\
**Post date:** [September 13, 2001, 3:05am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/5 "2001-09-13T03:05:11Z")

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x+x^2=800  
x^2 + x - 800 = 0

a_x^2 + b_x + c = 0 where

a = 1  
b = 1  
c = -800

The quadratic formula is

x = (-b +/- sqrt(b^2 - 4_a_c))/(2\*a)

Plugg’n and chugg’n gives you two real answers (rounded to the Eighth decimal place):

x = 27.78869032  
x = -28.78869032

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**Author:** ![Sterra](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@Sterra](https://boards.straightdope.com/u/Sterra)\
**Post date:** [September 13, 2001, 4:11am UTC](https://boards.straightdope.com/t/algebra-is-it-possible-to/81241/6 "2001-09-13T04:11:03Z")

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> [@](#):
>
> BTW, Sterra, the answer to your question in General Questions has been posted. Hadn’t you better getting to your homework?

I was going to respond to this thread earlier, but I forgot that it existed:) Thanks for the help.