Simplify the following rational expression:
25 - x^2/x^2 -3x - 10
According the the BEDMAS rules, the expression you posted simplifies to
25-1-3x-10
=14-3x
which is probably not what is intended.
All fractions have implicit parentheses on the numerator and denominator. You have probably omitted to insert them when you transcribe the expression to a single line, in which case parentheses are required.
Assuming the expression is
(25 - x^2)/(x^2 -3x - 10)
this can be factorized into
(5+x)(5-x)/((x-5)(x+2))
if x≠5, we can cancel (5-x)=-(x-5) and (x-5) leaving a negative sign.
So the final answer would be
-(5+x)/(x+2)