If f(1)=9 and f(n)= −2f(n−1) then find the value of f(6)

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Susie wants to take her friend out for lunch. she wants to spend $9.75 each person. how much will she spend in all.

Apassenger train and a freight train leave san jose at 3pm, traveling in the same direction. the passenger train is going three times as fast as the freight train. at 6pm they are 240 miles apart. how fast is each travelling? explain your answer and show your