I hope this question goes here.

Heres my question:

The line y-2x+u=0 is 2sqrt5 units from the point (1,-3). Find the possible values of u.

Here is my attempt:

y-2x+u

((-3)-2(1)+u)/√(2^2+1^2 )=2√5

(-5+u)/√5×√5/1=(2√5)/1×√5/1

-5+u=10

u=15 Or u=?

I hope that makes sense, sorry about the mess I dont know how to use the program here.

I can't find the other answer, but I know that the answer is u=15 or u=-5.

Thanks.