If cosx=-3/7, find the value for cos4x

How do i solve using pythagorean theorem?

The only way to identify an intercept is as an ordered pair. true false

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?