1.

Solve for x the equation 2^x + 3 = 5^x + 2.(a) ln (24/8)(b) ln (25/8) / ln (2/5)(c) ln (32/5) / ln (2/3)(d) ln (3/25)I had been asked this question in my homework.The doubt is from Discrete Probability in division Discrete Probability of Discrete Mathematics

Answer» RIGHT choice is (B) ln (25/8) / ln (2/5)

Easiest EXPLANATION: Given that 2^x + 3 = 5^x + 2. By taking ln of both SIDES: ln (2^x + 3) = ln (5^x + 2)

⇒(x + 3) ln 2 = (x + 2) ln 5

⇒x ln 2 + 3 ln 2 = x ln 5 + 2 ln 5

⇒x ln 2 – x ln 5 = 2 ln 5 – 3 ln 2

⇒ x = ( 2 ln 5 + 3 ln 2 ) / (ln 2 – ln 5) = ln (5^2 / 2^3) / ln (2/5) = ln (25/8) / ln (2/5).


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