differential equation: Show that if f and f' are continuous on a ≤ x ≤ b then f and f' are linearly independent on a ≤ x ≤ b

Show that if f and f' are continuous on a ≤ x ≤ b and f(x) is not zero for all x on a ≤ x ≤ b,
then f and xf are linearly independent on a ≤ x ≤ b.

Growth problems: mold grows at a rate proportional to its present size

A mold grows at a rate proportional to its present size. Initially there is 2 oz of this mold,
and two days later there is 3 oz. Find (a) how much mold was present after one day and (b)
how much mold will be present in ten days.
pls answer this probem..