(x² - 25) / (x2 - 3x - 10)
1) Expand the 1st factor: (x² - 25) = (x-5)(x+5)
2) factorize the 2nd: (x2 - 3x - 10), it's a quadratic equation with 5 & -2 as roots.
Then (x2 - 3x - 10) = (x-5)(x+2)
3) replace the latter in (x² - 25) / (x2 - 3x - 10)
===>(x-5)(x+5) / (x-5)(x+2)==>after simplifying Numerator & Denominator we
will get :(x+5) / (x+2)