Question

If $$P\left( n \right):{3^n} < n!,n \in N,$$     then $$P\left( n \right)$$  is true

A. for $$n \geqslant 6$$
B. for $$n \geqslant 7$$  
C. for $$n \geqslant 3$$
D. for all $$n$$
Answer :   for $$n \geqslant 7$$
Solution :
Given that, $$P\left( n \right):{3^n} < n!$$    Now, $$P\left( 7 \right):{3^7} < 7!$$    is true
$$\eqalign{ & {\text{Let, }}P\left( k \right):{3^k} < k! \cr & \Rightarrow P\left( {k + 1} \right):{3^{k + 1}} \cr & = 3 \cdot {3^k} < 3 \cdot k! < \left( {k + 1} \right)!\,\,\left( {\because k + 1 > 3} \right) \cr} $$

Releted MCQ Question on
Algebra >> Mathematical Induction

Releted Question 1

If $${a_n} = \sqrt {7 + \sqrt {7 + \sqrt {7 + ......} } } $$       having $$n$$ radical signs then by methods of mathematical induction which is true

A. $${a_n} > 7\,\,\forall \,\,n \geqslant 1$$
B. $${a_n} < 7\,\,\forall \,\,n \geqslant 1$$
C. $${a_n} < 4\,\,\forall \,\,n \geqslant 1$$
D. $${a_n} < 3\,\,\forall \,\,n \geqslant 1$$
Releted Question 2

Let $$S\left( k \right) = 1 + 3 + 5 + ...... + \left( {2k - 1} \right) = 3 + {k^2}.$$          Then which of the following is true

A. Principle of mathematical induction can be used to prove the formula
B. $$S\left( k \right) \Rightarrow S\left( {k + 1} \right)$$
C. $$S\left( k \right) ⇏ S\left( {k + 1} \right)$$
D. $$S(1)$$  is correct
Releted Question 3

If \[A = \left[ {\begin{array}{*{20}{c}} 1&0\\ 1&1 \end{array}} \right]{\rm{and }}\,\,I = \left[ {\begin{array}{*{20}{c}} 1&0\\ 0&1 \end{array}} \right],\]      then which one of the following holds for all $$n \geqslant 1,$$  by the principle of mathematical induction

A. $${A^n} = nA - \left( {n - 1} \right)I$$
B. $${A^n} = {2^{n - 1}}A - \left( {n - 1} \right)I$$
C. $${A^n} = nA + \left( {n - 1} \right)I$$
D. $${A^n} = {2^{n - 1}}A + \left( {n - 1} \right)I$$
Releted Question 4

The inequality $$n! > 2^{n - 1}$$   is true for

A. $$n > 2$$
B. $$n \in N$$
C. $$n > 3$$
D. None of these

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