Question 286256
Let 2^a = 5 and 2^b = 7. Using exponent rules, solve the equation in terms of a and b. 
0.4^x=343
[2^2/2*5]^x = 7^3
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Rewrite in terms of a and b:
(2^2/(2*2^a))^x = (2^b)^3
(2^2/2(a+1))^x = 2^(3b)
(2^(1-a))^x = 2^(3b)
(2^(x(1-a)) = 2^3b
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Equate the exponents and solve for "x":
x(1-a) = 3b
x = (3b)/(1-a)
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Cheers,
Stan H.
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