Weak Induction
(1) Using weak induction, prove that 3" < n! for all integers n > 6.
(2) Prove that log(n!) < n log(n) for all integers n > 1.
Reminder 1: log(1) = 0.
Reminder 2: log(a*b) = log(a) + log (6).
Reminder 3: If a < b then log(a) < log(6).
Note: The base of the logarithms doesn't matter for any of the above.
(3) Prove for all integers n > 1 that if A1, A2, ..., An and B are sets, then:_______.
(A1∩A2∩...∩An)UB = (A1UB)∩(A2UB)∩...∩(AnUB)
Hint: Use the fact that (XNY) UZ = (XUZ)n(Y UZ) where X, Y, and Z are sets.

Respuesta :

Answer:

Following are the answer to this question:

Explanation:

In option 1:

The value of n is= 7, which is (base case)

[tex]\to 3^7<7!\\\to 2187<5050\\[/tex]

when n=k for the true condition:

[tex]\to 3^k<k!......(i)\\\\[/tex]

when n=k+1 it tests the value:

[tex]\to 3^{(k+1)}= 3^k,3\\\to < (k!) 3 \ substituting \ equation \\\to <k! \cdot (k+1)\\[/tex]

since k>6  hence the value is KH>3 hence proved.

In option 2:

when:

for n=1:(base case)

[tex]\log(1!)<=1\log(1)[/tex]

0<=0 \\ condition is true

when the above statement holds value n=1

when n=k

[tex]\log(k!) <=k\log(k)....(1)[/tex]

when n=k+1

[tex]\log(k+1)!=\log(k!)+\log(k+1)\\[/tex]

              [tex]<= k \log(k)+\log(kH)\\<= kH\log(kH)\\[/tex]

[tex]\because k \log k<=k log(KH)\\\\[/tex]      [tex][\therefore KH>K \Rightarrow \log(KH>\loK)][/tex]

In option 3:

when n=1:

[tex]A_1 \cup B=A_1 \cup B\\\\[/tex]

when n=k

[tex]\to (A_1\cap A_2 \cap.....A_k) \cup B\\=(A_1\cup B) \cap(A_2\cup B_2)....(A_k \capB).....(a)\\\to n= k+1\\ \to (A_1\cap A_2 \cap.....A_{kH}) \cup B= (A_1\cup B)\\\\\to [(A_1\cap A_2 \cap.....A_{k}) \cup B]\cap (A_{KH}\cup B)\\\\\to [(A_1\cup B) \cap (A_2 \cup B) \cap (A_3\cup B).....(A_k\cup B)\cap (A_{k+1} \cup B)\\\\ \ \ \ \ \ \ substituting \ equation \ a \\\\[/tex]

hence n=k+1 is true.