Math
posted by Tim .
Give the equation of a line perpendicular to the line y = 4x having the same yintercept.

we won't do your homework or tests for you. We will critique your work.

I don't even know where or how to start.Im lost on these.

This is a test your teacher gave you. If you don't know where to start, you need to fail it. Getting answers from others will just put you in a deeper hole. Discuss this situation with your teacher.

The series of questions you asked are routine questions.
If you are finishing a semester and are reviewing for exams, you should know how to do these.
For the above question,
 how are slopes of perpendicular lines related ?
 what point is associated with the yintercept of an equation of the form
y = mx + b ? 
The y intercept of your y = 4x line is zero, and since the second line also has that y intercept, both lines must go through the origin (0,0).
The product of the slopes (m) for the two lines must be 1, if they are perpendicular. The first line has a slope of 4. You should be able to figure out the rest of it.