Here are the solutions to the problems.
Examples: Evaluate
a) Evaluate 5!
Step 1: Expand the factorial.
5!=5×4×3×2×1
Step 2: Calculate the product.
5!=120
The value is 120.
b) Evaluate 5!8!
Step 1: Expand the numerator until the denominator's factorial.
5!8!=5!8×7×6×5!
Step 2: Cancel out the common factorial.
5!8×7×6×5!=8×7×6
Step 3: Calculate the product.
8×7×6=336
The value is 336.
c) Evaluate (9−6)!(10−3)!
Step 1: Simplify the expressions inside the factorials.
(10−3)!=7!
(9−6)!=3!
Step 2: Substitute the simplified factorials into the expression.
3!7!=3!7×6×5×4×3!
Step 3: Cancel out the common factorial.
7×6×5×4=840
The value is 840.
d) Evaluate (n−3)!(n−1)!
Step 1: Expand the numerator until the denominator's factorial.
(n−3)!(n−1)!=(n−3)!(n−1)(n−2)(n−3)!
Step 2: Cancel out the common factorial.
(n−1)(n−2)
The value is (n−1)(n−2).
e) Evaluate n+2(n+2)!
Step 1: Expand the numerator.
n+2(n+2)!=n+2(n+2)(n+1)!
Step 2: Cancel out the common term.
(n+1)!
The value is (n+1)!.
f) If 7!1+8!1=9!x, find the value of x.
Step 1: Find a common denominator for the left side, which is 9!.
7!1=7!×8×91×8×9=9!72
8!1=8!×91×9=9!9
Step 2: Substitute these into the equation.
9!72+9!9=9!x
Step 3: Combine the terms on the left side.
9!72+9=9!x
9!81=9!x
Step 4: Since the denominators are equal, the numerators must be equal.
x=81
The value of x is 81.
Examples: Exponent of a Prime P in (n)!
The exponent of a prime p in n! is given by Legendre's formula:
Ep(n!)=∑k=1∞⌊pkn⌋=⌊pn⌋+⌊p2n⌋+⌊p3n⌋+…
a) Find the exponent of 5 in 50!
Step 1: Apply Legendre's formula for p=5 and n=50.
E5(50!)=⌊550⌋+⌊5250⌋+⌊5350⌋+…
E5(50!)=⌊550⌋+⌊2550⌋+⌊12550⌋+…
Step 2: Calculate the floor values.
E5(50!)=10+2+0+…
Step 3: Sum the values.
E5(50!)=12
The exponent of 5 in 50! is 12.
b) Find the exponent of 3 in 10!
Step 1: Apply Legendre's formula for p=3 and n=10.
E3(10!)=⌊310⌋+⌊3210⌋+⌊3310⌋+…
E3(10!)=⌊310⌋+⌊910⌋+⌊2710⌋+…
Step 2: Calculate the floor values.
E3(10!)=3+1+0+…
Step 3: Sum the values.
E3(10!)=4
The exponent of 3 in 10! is 4.
c) Find the exponent of 7 in 343!
Step 1: Apply Legendre's formula for p=7 and n=343.
E7(343!)=⌊7343⌋+⌊72343⌋+⌊73343⌋+⌊74343⌋+…
E7(343!)=⌊7343⌋+⌊49343⌋+⌊343343⌋+⌊2401343⌋+…
Step 2: Calculate the floor values.
E7(343!)=49+7+1+0+…
Step 3: Sum the values.
E7(343!)=57
The exponent of 7 in 343! is 57.
d) What is the highest power of 7 that can divide 5000! without leaving a remainder?
This is equivalent to finding the exponent of 7 in 5000!.
Step 1: Apply Legendre's formula for p=7 and n=5000.
E7(5000!)=⌊75000⌋+⌊725000⌋+⌊735000⌋+⌊745000⌋+⌊755000⌋+…
E7(5000!)=⌊75000⌋+⌊495000⌋+⌊3435000⌋+⌊24015000⌋+⌊168075000⌋+…
Step 2: Calculate the floor values.
E7(5000!)=714+102+14+2+0+…
Step 3: Sum the values.
E7(5000!)=832
The highest power of 7 that can divide 5000! is 7832.
The highest power is 832.
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