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April 11th, 2008, 06:46 AM   #1
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Permutation or combination??

Hello every one

I am a new member and I am happy to join this good forum


actually I need your help

I have the following problem and I am confused

so can you please help me solving it

Find the value of x in the following:
(a) x = 3nC35 – n + n + 18C3n

(b) 10 × x + 3Cx – 2 = x + 3P3
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April 11th, 2008, 09:59 AM   #2
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What's confusing? How far can you get?
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June 5th, 2008, 02:29 PM   #3
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The first one already gives you what x is. I think you might be having trouble because you might be thinking "I need a single number, not a whole expression". But keep in mind you have 4 variables. The first one can be simplified by first multiplying all the numbers of a single term, canceling n's out, and adding together like this:
[color=darkred]a) x= 105Cn + 54Cn
x= 159Cn
That's about as far as it can be simplified.[/color]
[color=darkblue]b) 10x + 3Cx – 2= x + 9P (9P=3P3)
To isolate x here, you can substract 9P
10x + 3Cx - 2 - 9P= x
You can factor this.
x= x(10 + 3C) - (2 + 9P)
You now substract x(10 + 3C), unfactor, and substract like terms.
-9x - 3Cx= -(2 + 9P)
Refactor (again!). I am doing all this factoring and unfactoring to
make you see how you can multiply and divide.
-x(9 + 3C)= -(2 + 9P)
Divide each side by -(9+3C).
x= -(2 + 9C)/-(9 + 3C)
x= (2 + 9C)/(9 + 3C)
x= (2 + 9C)/3(3+C)[/color]
Those would be your values. Can anyone check my answer for me?
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