I'll interpret it slightly differently:
(log 2x)^2 - 9.log x + 2 = 0
[(log 2) + (log x)]^2 - 9.log x + 2 = 0
Expanding that ^2 term,
(log 2)^2 + 2.log 2.log x + (log x)^2 - 9.log x + 2 = 0
Collecting terms,
(log x)^2 + (2.log 2 - 9).log x + (log 2)^2 + 2 = 0
Solving this quadratic in log x
log x = {-(2.log 2 - 9) ± √{(2.log 2 - 9)^2 - 4((log 2)^2 + 2)}} ÷ 2
log x = {-(2.log 2 - 9) ± √{4(log 2)^2 - 36.log 2 + 81 - 4(log 2)^2 - 8}} / 2
Reminder, log is log base e,
this gives us two values for log x, from which we can find x.
The values for x are roughly 1441 and roughly 1.5
I did work them out exactly and verified they solved the original equation, but I leave
the precise values up to the student to work out again as a calculator exercise.
log x = -log 2 + 9/2 ± √{-9.log 2 + 73/4}
lg^2(2x)-9lg(x)+2=0
I assume that this is...
ln (2x)^2 - 9 ln x + 2 = 0 .... so we have
2ln(2x) - 9 ln (x) + 2 = 0
2ln(2) + 2ln(x) - 9ln(x) + 2 = 0 factor
-7(ln x) = -2 - 2 ln(2) =
7 ln(x) = 2 + 2ln(2)
ln (x) = [2 + 2ln(2)] / 7
In exponential form, we have
e ^ ((2 + 2ln(2))/7) = x = about 1.622
I'll interpret it slightly differently:
(log 2x)^2 - 9.log x + 2 = 0
[(log 2) + (log x)]^2 - 9.log x + 2 = 0
Expanding that ^2 term,
(log 2)^2 + 2.log 2.log x + (log x)^2 - 9.log x + 2 = 0
Collecting terms,
(log x)^2 + (2.log 2 - 9).log x + (log 2)^2 + 2 = 0
Solving this quadratic in log x
log x = {-(2.log 2 - 9) ± √{(2.log 2 - 9)^2 - 4((log 2)^2 + 2)}} ÷ 2
log x = {-(2.log 2 - 9) ± √{4(log 2)^2 - 36.log 2 + 81 - 4(log 2)^2 - 8}} / 2
Reminder, log is log base e,
this gives us two values for log x, from which we can find x.
The values for x are roughly 1441 and roughly 1.5
I did work them out exactly and verified they solved the original equation, but I leave
the precise values up to the student to work out again as a calculator exercise.
log x = -log 2 + 9/2 ± √{-9.log 2 + 73/4}