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Find the value of m in 27−3×27−5=27−3m+1\frac{2}{7}^{-3}×\frac{2}{7}^{-5}=\frac{2}{7}^{-3m+1}72​−3×72​−5=72​−3m+1​​
Question

Find the value of m in 273×275=273m+1\frac{2}{7}^{-3}×\frac{2}{7}^{-5}=\frac{2}{7}^{-3m+1}​​

A.

5

B.

3

C.

–2

D.

–3

Correct option is B

Given:

(27)3×(27)5=(27)3m+1\left( \frac{2}{7} \right)^{-3} \times \left( \frac{2}{7} \right)^{-5} = \left( \frac{2}{7} \right)^{-3m+1}

Formula Used:

am×an=am+na^m \times a^n = a^{m+n}

Solution:
Combine exponents on the left-hand side:

(27)3×(27)5=(27)35=(27)8\left( \frac{2}{7} \right)^{-3} \times \left( \frac{2}{7} \right)^{-5} = \left( \frac{2}{7} \right)^{-3-5} = \left( \frac{2}{7} \right)^{-8}​​

Equating exponents:

8=3m+1 3m=81=9 m=93=3-8 = -3m + 1 \\\ -3m = -8 - 1 = -9 \\\ m = \frac{-9}{-3} = 3​​


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