The vertex of f(x)=-x2+4x-8 is (2, -4)
Bearing in mind that, there are
60 seconds in 1 minute,
60 minutes in 1 hr,
1000 meters in 1 km,
and 1.609 km in 1 mile
Since it starts at 12 and is increasing by 5 each time, the 70th term will be;
12 + 5(70)
12 + 350
362
362 is the 70th term of the sequence.
I'm not sure what your variables are, but I will try task 3 with you.
y=$500(in billions)
x= the number of years that have passed since 2009
percentage of decrease: 1 - % =
so your formula will look like this: y(1 - %)^x