Thread: log problem

2 Log(X) + Log 0.1 = Log 5 + Log 2
a a a a

i got X= 10 , and -10
i think all answers accepted because there is power 2 in 2 Log(X)so -10 won't be refused
is that right????

2 Log(X) + Log 0.1 = Log 5 + Log 2
2logx = log (10/0.1)
2logx = log100
2logx = 2
logx=1
x=10.

x cannot be -10 ,cause logy, y<0 ,is undefined

note log is a function that have unique sol only if there is

Originally Posted by johnnylam123

2 Log(X) + Log 0.1 = Log 5 + Log 2
2logx = log (10/0.1)
2logx = log100
2logx = 2
logx=1
x=10.

x cannot be -10 ,cause logy, y<0 ,is undefined

ok but 2Log X = Log X^2
so -10 will be 100 and Log 100 = 2???

x=-10 would fail the original equation.

2Log X = Log X^2 is a formula for positive x only.
In general,

With complex numbers, you can evaluate log(-10) (it is a complex number), but you cannot use the formula given above, as -10 is not [real and] positive.

Originally Posted by mido22

2 Log(X) + Log 0.1 = Log 5 + Log 2
a a a a

Is the actual problem

Originally Posted by Plato

Is the actual problem

no it is without brackets

Originally Posted by mido22

no it is without brackets

What brackets?

Are you talking parenthesis, .
If you are you need to know that it is incorrect to write .
That is function notation. Just as we write , we also write

even it is loga, results is the same