We'll change the base 4 of the logarithm into the base 2:
log[base 4](x-1) = log[base 2](x-3)
log 2 (x-1) = log 4 (x-1)*log 2 (4)
But log 2 (4) = log 2 (2^2)
We'll apply the power property of logarithms and we'll get:
log 2 (2^2) = 2*log 2 (2)
But log 2 (2) = 1
log 2 (2^2) = 2
log[base 4](x-1) = log[base 2](x-1)/2
The equation will become:
{log[base 2](x-1)}/2 = log[base 2](x-3)
log[base 2](x-1) = 2*log[base 2](x-3)
log[base 2](x-1) = log[base 2][(x-3)^2]
We'll apply one to one property:
x-1 = (x-3)^2
We'll expand the square:
x-1 = x^2 - 6x + 9
We'llmove all terms to one side:
x^2 - 7x + 10 = 0
We'll apply the quadratic formula:
x1 = [7+sqrt(49-40)]/2
x1 = (7+3)/2
x1 = 5
x2 = (7-3)/2
x2 = 2
Now, we'll check if the found solutions are convenient and respect the constraints of existence of logarithms above:
The constraints of existence of logarithms are:
x-1>0
x>1
x-3>0
x>3
So, all solutions have to be more than the value 3.
Because the second solution, x2=2<3, is not acceptable, so the only solution of the equation is x=5.
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