Ok I'm a little confused with this: 16x-y^4=0 When you solve for (y) you get: y= plus/minus 4th root(16x) right? There for it isn't a function. What about y=sq.rt.(1-x)? Does it have the plus/minus automatically? Do you only put the plus/minus sign if you solve for y? I just don't get when you have to put the plus/minus in front of the sq.rt. Do you always have to put one there? or only if you solve for y, etc.?