Question

Let the sequence $$ < {b_n} > $$  of real numbers satisfies the recurrence relation $${b_{n + 1}} = \frac{1}{3}\left( {2{b_n} + \frac{{125}}{{b_n^2}}} \right),\,{b_n} \ne 0.$$       Then find $$\mathop {\lim }\limits_{n \to \infty } \,{b_n}.$$

A. $$10$$
B. $$15$$
C. $$5$$  
D. $$25$$
Answer :   $$5$$
Solution :
$$\eqalign{ & {\text{Let }}\mathop {\lim }\limits_{n \to \infty } \,{b_n} = b \cr & {\text{Now, }}{b_{n + 1}} = \frac{1}{3}\left( {2{b_n} + \frac{{125}}{{b_n^2}}} \right) \cr & {\text{or }}\mathop {\lim }\limits_{n \to \infty } {b_{n + 1}} = \frac{1}{3}\left( {2\mathop {\lim }\limits_{n \to \infty } {b_n} + \frac{{125}}{{\mathop {\lim }\limits_{n \to \infty } b_n^2}}} \right) \cr & {\text{or }}b = \frac{1}{3}\left( {2b + \frac{{125}}{{{b^2}}}} \right) \cr & \Rightarrow \frac{b}{3} = \frac{{125}}{{3{b^2}}} \cr & \Rightarrow {b^3} = 125{\text{ or }}b = 5 \cr} $$

Releted MCQ Question on
Calculus >> Limits

Releted Question 1

lf $$f\left( x \right) = \sqrt {\frac{{x - \sin \,x}}{{x + {{\cos }^2}x}}} ,$$     then $$\mathop {\lim }\limits_{x\, \to \,\infty } f\left( x \right)$$    is-

A. $$0$$
B. $$\infty $$
C. $$1$$
D. none of these
Releted Question 2

If $$G\left( x \right) = - \sqrt {25 - {x^2}} $$     then $$\mathop {\lim }\limits_{x\, \to \,{\text{I}}} \frac{{G\left( x \right) - G\left( I \right)}}{{x - 1}}$$     has the value-

A. $$\frac{1}{{24}}$$
B. $$\frac{1}{{5}}$$
C. $$ - \sqrt {24} $$
D. none of these
Releted Question 3

$$\mathop {\lim }\limits_{n\, \to \,\infty } \left\{ {\frac{1}{{1 - {n^2}}} + \frac{2}{{1 - {n^2}}} + ..... + \frac{n}{{1 - {n^2}}}} \right\}$$        is equal to-

A. $$0$$
B. $$ - \frac{1}{2}$$
C. $$ \frac{1}{2}$$
D. none of these
Releted Question 4

If $$\eqalign{ & f\left( x \right) = \frac{{\sin \left[ x \right]}}{{\left[ x \right]}},\,\,\left[ x \right] \ne 0 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\, = 0,\,\,\,\,\,\,\,\,\,\,\,\,\,\left[ x \right] = 0 \cr} $$
Where \[\left[ x \right]\] denotes the greatest integer less than or equal to $$x.$$ then $$\mathop {\lim }\limits_{x\, \to \,0} f\left( x \right)$$   equals

A. $$1$$
B. $$0$$
C. $$ - 1$$
D. none of these

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