easy maths problem, but different opinions

[kahyang]

I just wanted to ask, the simpliest question, yet people tell me different answers.

If a question ask like this, in C1 for AS MAthematics

What is the answer for 25^1/2 ? ( square root of 25 )

is the answer 5 or plus-minus 5? MY teacher in college tells me its only 5, but answers in see in text book is plus-minus 5. can anyone enlighten me on this ? thanks

[ExamSolutions]

√16 means 'the positive square root of 16'
So √16 = 4 only and not ±4

However when solving an equation such as x = 16 then the solutions are -4 and 4.
You would write x=±√16

Using the index ½ is the same as using the positive square root only.

So 16^ ½ = √16 = 4