When do you use plus/minus signs with roots?

  • Context: High School 
  • Thread starter Thread starter AznBoi
  • Start date Start date
  • Tags Tags
    Confused
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
2 replies · 3K views
AznBoi
Messages
470
Reaction score
0
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.?
 

Discussion

Mathematics news on Phys.org
Well, the even root of a number is DEFINED to be the positive number.
That is, by definition, [itex]\sqrt{1-x}[/itex] is a positive number.

When you solve for y, however, you must remember that not only do you have the positive, even root as a solution, but also the negative of that number.
 
Oh ok. So if they give you an equation that has no plus/minus infront of it, then the equation is POSITIVE. However, if you solve for y and get a sq.rt. then you must put the plus/minus sign right? Thanks.