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Rational roots - standard form of equation

by Janinever
Tags: equation, form, rational, roots, standard
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Janinever
#1
Dec27-12, 07:00 AM
P: 13
Hi everybody!

I've hit a blank with regards to this 1 equation on a old exam paper - think I've overloaded myself a bit and just feel a bit like a airhead at the moment!

I understand the actual method and getting to the answer but it starts off with a equation which you then need to get to a standard form to use the formula to check if the roots are rational.

The initial equation is this :

4x^2 + 2kx - k = 2x

Then on the memorandum this is taken to standard form so the info can be substituted into the formula Δ = b^2 - 4ac

the standard form they then write that initial equation in is :

4x^2 + 2(k-1)x-k = 0

How do they get from 4x^2 + 2kx - k = 2x to this 4x^2 + 2(k-1)x-k = 0

The rest I understand entirely. Literally just the above has be scratching my head!

Please help :)

Thank you!
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pwsnafu
#2
Dec27-12, 07:06 AM
Sci Advisor
P: 833
Quote Quote by Janinever View Post
How do they get from 4x^2 + 2kx - k = 2x to this 4x^2 + 2(k-1)x-k = 0
Sometimes you overlook the obvious answers. Just subtract 2x from both sides.
Janinever
#3
Dec27-12, 07:14 AM
P: 13
Thank you!


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