Question

(4) 20-^x = 1/7 हो तो (20)²^x का मान है -:
(a) 1/49
(b) 7
(c) 49
(d) 1​

Answer 1

Answer:

20-^x = 1/7

${20}^{ - x} = \frac{1}{7} \\ \frac{1}{ {20}^{x} } = \frac{1}{7} \\ \\ {20}^{x} = 7$

Squaring both side -

${20}^{2x} = {7}^{2} = 49$

answer (c) 49