If I'm not wrong, all you have to do is use the distributive property.
I=k/d^2
4=k/d^2 and 1=k/64 so if we divide the first by the second we get:
4/1=(k/d^2)/(k/64)
4=(k/d^2)*(64/k)
4=64/d^2
d^2=64/4
d^2=16
d=4 meters
Consider the equation:

Subtracting '4' from both the sides of the equation, we get as


Squaring on both the sides of the equation, we get


Subtracting '2' from both the sides of the equation, we get

x=14
Since, An extraneous solution is a solution that arises from the solving process that is not really a solution at all. But, in this equation x=14 is the solution of the given equation.
Hence, it is not an extraneous solution.
You have to move your variables around.<span />