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Finding x value from this quadratic

So I have 2 - (1/x) = -(1/4)x + (1/8)
and I want to find the x value

so at first I tried to just do the normal adding and subtracting and I got
-1 + (1/4)x^2 + 15/8 = 0

Still though, I had no idea how to solve that.

Then, I tried this:


And this is wrong too.

I'm stuck. The answer is apparently 2x^2 + 15x - 8 = 0
But I have no idea how they got there.

Help please :3
Not sure how you removed that x in the denominator. Multiply both sides by x so its not in the denominator.
Reply 2
Avatar for Alex621
Alex621
17
Original post by frostyy
So I have 2 - (1/x) = -(1/4)x + (1/8)
and I want to find the x value

so at first I tried to just do the normal adding and subtracting and I got
-1 + (1/4)x^2 + 15/8 = 0

Still though, I had no idea how to solve that.

Then, I tried this:


And this is wrong too.

I'm stuck. The answer is apparently 2x^2 + 15x - 8 = 0
But I have no idea how they got there.

Help please :3


I would begin by multiplying everything by 8x
20160412_213044.jpghey i hope my working makes sense but i just multiplied each fraction out each time
Original post by frostyy
So I have 2 - (1/x) = -(1/4)x + (1/8)
and I want to find the x value

so at first I tried to just do the normal adding and subtracting and I got
-1 + (1/4)x^2 + 15/8 = 0

Still though, I had no idea how to solve that.

Then, I tried this:


And this is wrong too.

I'm stuck. The answer is apparently 2x^2 + 15x - 8 = 0
But I have no idea how they got there.

Help please :3

2 - (1/x) = -(1/4)x + (1/8) multiply by 816 - (8/x) = - 2x + 1 multiply by x16x - 8 = - 2x^2 + x rearrange
2x^2 +15x - 8 = 0
(edited 8 years ago)
Original post by DotDotDot...
2 - (1/x) = -(1/4)x + (1/8) multiply by 816 - (8/x) = - 2x + 1 multiply by x16x - 8 = - 2x^2 + x rearrange
2x^2 +15x - 8 = 0 factorise
(2x - 1)(x + 8) = 0 solve
x = 1/2 x = - 8


Why are you handing over answers?
Original post by Vikingninja
Why are you handing over answers?

Why do you care?
Sometimes its just as helpful to be shown a fully worked answer so you know how to do the next one. Its not life or death here.
Reply 7
Avatar for Zacken
Zacken
22
Original post by DotDotDot...
Why do you care?
Sometimes its just as helpful to be shown a fully worked answer so you know how to do the next one. Its not life or death here.


Please edit or remove your post or I'll have to. Full solutions are against forum guidelines.
Original post by Zacken
Please edit or remove your post or I'll have to. Full solutions are against forum guidelines.

Fine, sorry I didn't know it was against the rules.

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