Question

please explain?.....plzzzz

Answer 1

16.

$a = 243 \\ \\ r = \frac{81}{243} = \frac{1}{3} \\ \\ \\ T_{15} = ar^{14} \\ \\ = 243 \times (\frac{1}{3})^{14} \\ \\ = 3^5 \times 3^{- 14} \\ \\ = 3^{5 - 14} \\ \\ = 3^{- 9} \\ \\ = (\frac{1}{3})^9$

Option (a) is an answer.

$(\frac{1}{3})^9 \\ \\ = (\frac{1}{3})^{10 - 1} \\ \\ = (\frac{1}{3})^{10} \times (\frac{1}{3})^{- 1} = (\frac{1}{3})^{10} (\frac{1}{3})^{- 1}$

Option (c) is another answer.

Options (a) and (c) are the answers.

17.

(a) - Not GP, it's an AP. The first term 2 is added up by the common difference 2. A. E. = 2n

(b) - It's a GP. The first term 5 is multiplied up by the common ratio 5. A. E. = 5^n

(c) - It's a GP. The first term 1.5 is multiplied up by the common ratio 2. A. E. = 3 × 2^(n - 2)

(d) - Not GP, it's an AP. The first term 8 is added up by the common difference 8. A. E. = 8n

A. E. means algebraic expression.

(a) and (d) are the answers.

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