Asked by Shawn
Where appropriate, include the approximation to the nearest ten-thousandth.
31.) log(x-4)+ log(x+4)= log4
I have the answer as 4
Is this answer right?
31.) log(x-4)+ log(x+4)= log4
I have the answer as 4
Is this answer right?
Answers
Answered by
bobpursley
log a + log b is same as log ab
so log(x^2-4)=log4
taking antilogs
x^2-4=4 solve for 4
check my thinking.
so log(x^2-4)=log4
taking antilogs
x^2-4=4 solve for 4
check my thinking.
Answered by
Shawn
Okay x^2-4 = 4
x^2= 8
sqrt(x^2)= sqrt 8
x= 2.83 is this right?
Answered by
Reiny
log k has a nasty habit of becoming undefined if k is not positive.
you answer of x = 2.832 is correct according to the steps taken, but...
when we sub into log (x-4) we get log (-1.168 which is undefined,
so there is no solution in the set of real numbers for your equation
you answer of x = 2.832 is correct according to the steps taken, but...
when we sub into log (x-4) we get log (-1.168 which is undefined,
so there is no solution in the set of real numbers for your equation
Answered by
Reiny
Going back and looking over the previous solutions, I noticed that the original non-log equation should have said:
x^2-16 = 4
so x^2 = 20
x = √20 = 4.472136
which works upon substituting.
x^2-16 = 4
so x^2 = 20
x = √20 = 4.472136
which works upon substituting.
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