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Big Ideas Math Geometry, 2014

BI

Big Ideas Math Geometry, 2014 View details

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Exercise 5 Page 717

Recall the formula for a combination, _n C_r = n!/(n-r)! r!.

20

Practice makes perfect

To evaluate the given combination, we will use the corresponding formula. _n C_r = n!/(n-r)! r! We are given that n=6 and r=3. Let's substitute these values into the formula.

_n C_r = n!/(n-r)! r!

n= 6, r= 3

_6 C_3 = 6!/( 6- 3)! 3!

Subtract term

_6 C_3 = 6!/3! 3!

Write as a product

_6 C_3 = 6* 5* 4* 3!/3! 3!

a/b=.a /3!./.b /3!.

_6 C_3 = 6* 5* 4/3!

Write as a product

_6 C_3 = 6* 5* 4/3* 2* 1

Multiply

_6 C_3 = 120/6

a/b=.a /6./.b /6.

_6 C_3 = 20/1

a/1=a

_6 C_3 = 20

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Exercises p.717