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Math majors...need your help

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Old Oct 17, 2004 | 04:24 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 Oct 17, 2004 | 04:48 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 Oct 17, 2004 | 05:14 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 Oct 17, 2004 | 05:22 PM
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I got X=64 but I'm old and rusty
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Old Oct 17, 2004 | 05:34 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 Oct 17, 2004 | 05:37 PM
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Yes, don't factor it. Use the quadratic formula. Much easier.
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Old Oct 17, 2004 | 06:18 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 Oct 17, 2004 | 06:28 PM
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Ooh, good point. Always remember to check all possible solutions... unlike me.
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Old Oct 17, 2004 | 07:27 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 Oct 17, 2004 | 07:29 PM
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So that would make +64 an answer.

Checks work (again)... Looks good.
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