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Factorials
CONCEPTS
Equation
• n ! = (n - 0) (n - 1) (n - 2)…
EXAMPLES
• 4 ! = (4 - 0) (4 - 1) (4 - 2) (4 - 3) = 4 * 3 * 2 * 1 = 24
PRACTICE PROBLEMS
Question 1 For all positive integers a & b, the expression (a!)ᵇ is equivalent to which expression?
1. (aᵇ)!
2. (ab)!
3. b (a!)
4. aᵇ (-1 + -2 + -3 + …)
5. [a (a - 1)(a - 2) … (1)]ᵇ
-- Answer -- [a (a - 1)(a - 2)...1]ᵇ
3! = 3 * 2 * 1
a! = a (a - 1) ( a - 2)…1
(a!)ᵇ = [a (a - 1)(a - 2)...1]ᵇ
ACT PRACTICE PROBLEMS
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