Question

if 11Cx=11C2x-4 and × not=4 find 7Cx

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Answer 1

Answer:

21

Step-by-step explanation:

11cx=11c2x-4

=>11=x+2x-4

=>11=3x-4

=>3x=15

=>x=5

Now

7cx

=7c5

=7!/5!×2!

=7×6×5!/5!×2

=7×3

=21

Answer 2

The correct answer is x = 5 and the value of $^{7} C5$ is 21.

Given: The equation = $^{11} C_{x} =^{11} C_{2x-4}$.

To Find: The value of $^{7} Cx$.

Solution:

We have two option either the bases of both the terms are equal or sum of bases of both the terms is 11.

So,

x = 2x - 4

x = 4 (x cannot be 4 as given in question)

x + 2x - 4 = 11

3x = 15

x = 5

$^{7} Cx$ = $^{7} C5$ = $\frac{7!}{5!2!}$

= 21

Hence, the value of x is 5 and the value of $^{7} C5$ is 21.

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