Someone me now. and i want the right answer

For the function, f(x) = -5x 2, find f(-4).

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

What is this inequality notation? t is less then or equal to 2