Quadratic with fractions - completing the square or formula

Doing past papers at the mo & have a quadratic which I am stuck on

find fixed points of f(x) = x^2+(13/12)x-1/2

Now, fixed points are when f(x) = x, so I have subtracted x from both sides

=> x^2 + (1/12)x - 1/2 = 0 to make an easier(?) quadratic

so a=1, b=1/12 & c=-1/2

Sub into formula & I am now stuck as the sqrt comes up as negative & I'm not sure enough about completing the square.

I also have similar equation f(x) = x^2 + (14/15)x - 2/5. Stuck here, too (Speechless)

Would appreciate a little help.

Thank you

Re: Quadratic with fractions - completing the square or formula

You can also multiply both sides by 12 to get

Re: Quadratic with fractions - completing the square or formula

Hi.

I have the second example, too, which I have still not been able to do. Similar equation f(x) = x^2 + (14/15)x - 2/5

Please could someone point me in the right direction with this, too. It is part of a fixed point iteration question.

I'm having trouble with that, too, but I must keep trying.

Re: Quadratic with fractions - completing the square or formula

Quote:

Originally Posted by

**froodles01** Doing past papers at the mo & have a quadratic which I am stuck on

find fixed points of f(x) = x^2+(13/12)x-1/2

Now, fixed points are when f(x) = x, so I have subtracted x from both sides

=> x^2 + (1/12)x - 1/2 = 0 to make an easier(?) quadratic

so a=1, b=1/12 & c=-1/2

Sub into formula & I am now stuck as the sqrt comes up as negative & I'm not sure enough about completing the square.

I also have similar equation f(x) = x^2 + (14/15)x - 2/5. Stuck here, too (Speechless)

Would appreciate a little help.

Thank you

Are you trying to find the x intercepts for the second? If so...

Re: Quadratic with fractions - completing the square or formula

Oooh! (Surprised) Ideal. This DOES make my understanding better (as well as having the answer). I'll get there one day.