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Question -

If┬аnC10┬а=┬аnC12,find┬а23Cn.



Answer -

We know that if┬аnCp┬а=┬аnCq,then one of the following conditions need to be satisfied:

(i) p = q

(ii) n = p + q

So from thequestion┬аnC10┬а=┬аnC12,we can say that

10 тЙа 12

So, the condition (ii)must be satisfied,

n = 10 + 12

n = 22

Now, we need tofind┬а23Cn,

We know the value of nso,┬а23Cn┬а=┬а23C22

Let us use theformula,

nCr┬а= n!/r!(n тАУ r)!

So now, value of n =23 and r = 22

nCr┬а= n!/r!(n тАУ r)!

23C22┬а= 23! / 22!(23 тАУ 22)!

= 23! / (22! 1!)

= [23├Ч22!] / (22!)

= 23

тИ┤┬аThe valueof┬а23C22┬а= 23.

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