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Math majors...need your help

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Old 10-17-2004, 05:24 PM
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Default Math majors...need your help

I'm shooting for a BC in computer science, hence I need to take numerous mathmatics courses. Well the sad part is I'm REALLY awful at factoring and I'm all the way into Business Calc at this point. So can someone please factor this one for me?

-x^2 - 36x + 6400 = 0

This is embarrassing.
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Old 10-17-2004, 05:48 PM
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Default Re: Math majors...need your help

Originally Posted by Allmachtige
I'm shooting for a BC in computer science, hence I need to take numerous mathmatics courses. Well the sad part is I'm REALLY awful at factoring and I'm all the way into Business Calc at this point. So can someone please factor this one for me?

-x^2 - 36x + 6400 = 0

This is embarrassing.
6400=x^2 + 36x

80 = x + 6x

80 = 7x

x=11.428.....

Probably wrong.
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Old 10-17-2004, 06:14 PM
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You lost an x.

x=-b (+ and -) SQRT(b^2-4ac)/2a

x = -100 and -64
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Old 10-17-2004, 06:22 PM
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I got X=64 but I'm old and rusty
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Old 10-17-2004, 06:34 PM
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Originally Posted by jwikoff99
You lost an x.

x=-b (+ and -) SQRT(b^2-4ac)/2a

x = -100 and -64
Where'd the b come from?

Never mind. I'm too old. My head hurts...... :P
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Old 10-17-2004, 06:37 PM
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Yes, don't factor it. Use the quadratic formula. Much easier.
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Old 10-17-2004, 07:18 PM
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jwikoff99 is right. The two possible solutions are -64 and -100, however, when you plug both in for x you will find that only -100 =0.
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Old 10-17-2004, 07:28 PM
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Ooh, good point. Always remember to check all possible solutions... unlike me.
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Old 10-17-2004, 08:27 PM
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If you factor it its -(x-64)(x+100)...but you could also use the quadratic formula to find it.
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Old 10-17-2004, 08:29 PM
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So that would make +64 an answer.

Checks work (again)... Looks good.
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