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The expression ""^n Cr+4 ""^n C(r-1) +...

The expression
`""^n C_r+4 ""^n C_(r-1) +6 ""^n C_(r-2) +4 ""^n C_(r-3)+""^n C(r-4)=`

A

`"^(n+4) C_r`

B

`2, "^(n+4) C_(r-1)`

C

`4. "^n C_r`

D

`11, "^n C_r`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the expression \[ {n \choose r} + 4 {n \choose r-1} + 6 {n \choose r-2} + 4 {n \choose r-3} + {n \choose r-4} \] we can use the properties of combinations and Pascal's identity. ### Step-by-Step Solution: 1. **Understanding the Expression**: We have a sum of combinations with different coefficients. The coefficients are 1, 4, 6, 4, and 1, which resemble the binomial coefficients from the expansion of \((x + y)^4\). 2. **Using Binomial Coefficients**: The coefficients can be recognized as: \[ {4 \choose 0}, {4 \choose 1}, {4 \choose 2}, {4 \choose 3}, {4 \choose 4} \] Thus, we can rewrite the expression as: \[ \sum_{k=0}^{4} {4 \choose k} {n \choose r-k} \] 3. **Applying Vandermonde's Identity**: According to Vandermonde's identity, we have: \[ \sum_{k=0}^{r} {m \choose k} {n \choose r-k} = {m+n \choose r} \] In our case, \(m = 4\) and \(n = n\). Therefore, we can apply this identity: \[ \sum_{k=0}^{4} {4 \choose k} {n \choose r-k} = {n+4 \choose r} \] 4. **Final Result**: Thus, the value of the original expression simplifies to: \[ {n+4 \choose r} \] ### Conclusion: The final answer to the expression is: \[ {n+4 \choose r} \]
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Prove that ""^(n)C_(r )+2""^(n)C_(r-1)+ ""^(n)C_(r-2)= ""^(n+2)C_(r ) .

If ([""^(n)C_(r) + 4*""^(n)C_(r+1) + 6*""^(n)C_(r+2)+ 4*""^(n)C_(r+3) + ""^(n)C_(r+4)])/([""^(n)C_(r) + 3. ""^(n)C_(r+1)+ 3*""^(n)C_(r+2) + ""^(n)C_(r +3)])=(n + lambda)/(r+lambda) the value of lambda is

""^(n)C_(r+1)+^(n)C_(r-1)+2.""^(n)C_(r)=

"^(n)C_(r)=^(n)C_(n-r)

If .^(n)C_(r-1) = 36, .^(n)C_(r) = 84 and .^(n)C_(r+1) = 126

""^(n)C_(n-r)+3.""^(n)C_(n-r+1)+3.""^(n)C_(n-r+2)+""^(n)C_(n-r+3)=""^(x)C_(r)

ML KHANNA-PERMUTATIONS AND COMBINATIONS -SELF ASSESSMENT TEST
  1. The expression ""^n Cr+4 ""^n C(r-1) +6 ""^n C(r-2) +4 ""^n C(r-3)+"...

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  2. sum(r=0)^m "^(n+r) Cn is equal to

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  3. A polygon has 44 diagonals , then the number of its sides is

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  4. If 7 points out of 12 are in the same straight line, then what is the ...

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  5. All the letters of the word EAMCET are arranged in all possible ways. ...

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  6. Out of 10 red and 8 white balls , 5 red and 4 white balls can be drawn...

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  7. 7 men and 7 women are to sit round a table so that there is a man on e...

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  8. The number of seven digit integers with sum of the digits equal to 10 ...

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  9. The total number of ways in which 5 balls of differ- ent colours can b...

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  10. Assuming the balls to be identical except for difference in colours, t...

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  11. How many different words can be formed by jumbling the letters of the ...

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  12. The number of numbers, that can be formed by using all digits 1,2, 3, ...

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  13. How many words can be formed with the letters o the word MATHEMATICS b...

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  14. In how many ways 7 men and 7 women can sit on a round table such that ...

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  15. If ^15 C(3r)=^(15)C(r+3) , then find rdot

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  16. IF ""^n C12=""^nC6 then "^n C2=

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  17. There are n points in a place in which p point are collinear. How many...

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  18. There are 10 points in a plane, out of these 6 are collinear. The numb...

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  19. IF x,y,r are positive integers then ""^x Cr+""^x C(r-1) . ""^ y C1+ ...

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  20. A dictionary is printed consisting of 7 lettered words only that can b...

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  21. Let Tn be the number of all possible triangles formed by joining ve...

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