How to find the lowest form of a fraction?

To find the lowest form of a fraction or simplifying you find a number that divide into the numerator(Top Number) and denominator(Bottom Number)

For example
4(Numerator)
_
16(Denominator

Both numbers can be divided by 4
4/4= 1
_ _
16/4=4

A way to check if your right is to divide both fractions you should get the same answer
4/16=0.25
1/4=0.25

(5q2 − r2s)(25q^4+5q^2r^2s+1r^4s^2)