SOLUTION: In 11!/r!(11,r)! - 6 = C(18,17), what is the value of r. Show the solution.

Algebra ->  Permutations -> SOLUTION: In 11!/r!(11,r)! - 6 = C(18,17), what is the value of r. Show the solution.      Log On


   

Question 1192505: In 11!/r!(11,r)! - 6 = C(18,17), what is the value of r. Show the solution.
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


The expression "(11,r)!" has no meaning. I will assume you mean "(11-r)!".

C%2818%2C17%29=C%2818%2C1%29=18

11%21%2F%28r%21%2811-r%29%21%29=C%2811%2Cr%29

Your equation is

11%21%2F%28r%21%2811-r%29%21%29-6=18
11%21%2F%28r%21%2811-r%29%21%29=C%2811%2Cr%29=24

The values of C(11,r) are 1, 11, 55, ....

There is no r for which C(11,r) = 24.

The problem as you show it is faulty.