Hi NinjaDevo,
You give great detailed answers along with showing how to check, that is really great.
However think about this step
6x2+5x-4=0
(3x + 4)(2x - 1) = 0
I think that for many people this is the step that causes the greatest amount of problems and you have not described how you did it.
Here is a you tube clip to show you how to do it.
https://www.youtube.com/watch?v=HvBiJ9W00Z4
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Some times it is easier just to use the quadratic forumla. (right from the beginning)
If you have problems remembering it this clip will help you.
https://www.youtube.com/watch?v=O8ezDEk3qCg
In this case a=6, b=5, c=-4