Which term of the following sequences: (a) 2, 2√2, 4,… is 128 ? (b) √3, 3, 3√3,… is 729 ?
Which term of the following sequences: (a) 2, 2√2, 4,… is 128 ? (b) √3, 3, 3√3,… is 729 ?

(i) The given arrangement,

    \[2,\text{ }2\surd 2,\text{ }4,\ldots \]

We have,

    \[a\text{ }=\text{ }2\text{ }and\text{ }r\text{ }=\text{ }2\surd 2/2\text{ }=\text{ }\surd 2\]

Taking the

    \[{{n}^{th}}\]

term of this arrangement as

    \[128\]

, we have

NCERT Solutions Class 11 Mathematics Chapter 9 ex.9.3 - 4

Accordingly, the thirteenth term of the given succession is

    \[128.\]

 

(ii) Given arrangement,

    \[\surd 3,\text{ }3,\text{ }3\surd 3,\ldots \]

We have,

    \[a\text{ }=\text{ }\surd 3\text{ }and\text{ }r\text{ }=\text{ }3/\surd 3\text{ }=\text{ }\surd 3\]

Taking the nth term of this arrangement to be

    \[729,\]

we have

NCERT Solutions Class 11 Mathematics Chapter 9 ex.9.3 - 5

Accordingly, the twelfth term of the given succession is

    \[729.\]