Algebra

By convention, we take the principal root which is +5, unless we are solving an equation involving the roots of 25. Then, both roots [positive and negative] are taken.

Thus

sqrt(25)  = 5

But

x^2  = 25

Then, 

x  =  +/- 5

?

What's the square root of 25 ?
Is it 5 or +/- 5 and why ?

ALSO

Say it was + or -

then there would be no way of differentiating between

9+sqrt(25)   and    10-sqrt(25)

They would both have the same 2 answers    9 + or - 5   =   14 or 4