(f^2 - 25)/5 * f/(f-5)
Factor the difference of squares:
(f-5)(f+5)/5 * f/(f-5)
Cancel "f-5" from numberator and denominator:
(f+5)/5 * f/1
Multiply fractions:
f(f+5)/5
Since this doesn't match any of the answers,
we should distribute the "f" in the numerator:
(f^2+5f)/5
Thus, the best answer of the selection is:
(B) (f^2-5f)/5