Calling FTR Math-Geeks

if y=x(x+1), what does x equal?

thankin' yew

350

don't you know your quadratic formula...

y = x(x+1) = x^2 + x
x^2 + x - y = 0
x = [-1 p/m (1^2 +4y)^(1/2) ] / 2

where p/m means plus or minus.

thus:
x = [-1 + (1+4y)^(1/2) ] / 2
or
x = [-1 - (1+4y)^(1/2) ] /2

where (1+4y)^(1/2) is solvable using real numbers only if y >= -0.25.

I was so close.

or by completing the square:

y=x^2 + x

1/2 of b squared where b is 1, so to complete the square would be 1/4

y+1/4=x^2 +x + 1/4

y+ 1/4= (x + 1/2) (x + 1/2)

y+ 1/4= (x + 1/2)^2

Sqrt(y+ 1/4)= x + 1/2

x= Sqrt (y +1/4) - 1/2 for real numbers y>= 1/4

Thanks Chaps

I'll go with 350. Seems a lot simpler

y=x^2+x - Wolfram|Alpha

Originally Posted by d0zer

y=x^2+x - Wolfram|Alpha

thanks d0ze

Wolfram Alpha is amazing!! I threw some of the most complicated equations and systems of equations at it when I was getting my physics degree. It not only handles them, it shows the work... Seriously, I'm not sure I'd be able to use the integral chain rule on my own without the repeated solutions offered to me by Wolfram Alpha.

Even better, though, is that you can type in just about anything into the search bar and get a page full of something. Try typing your first name into the search bar, for instance.

*physics high five*

Long time fan of the Feynman pic.

yes....enough with the geeking-out now, boys, thank you