10 *(10^x)^2 - 7 (10^x) = 26
let z = 10^x
10 z^2 - 7 z -26 = 0
( z - 2)( 10 z + 13) = 0
10^x = 2 or 10^x = -1.3
if you log is base 10
log 10^x = x = log 2
but if x = log a
then log a = log 2
so a = 2
similarly
log 10^x = x = log (-1.3) but not allowed :)
Given that x=lg a is a solution of the equation 10^(2x+1)-7(10^x) =26. Find the value of a.
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