HELP PLS Find the formula for the nth term of the sequence below.

20, −10, 5, −2.5, ...

a)an=−12⋅20nA sub n is equal to negative 1 half times 20 to the n th power

b)an=−12⋅20n−1A sub n is equal to negative 1 half times 20 raised to the n minus 1 power

c)an=20⋅(−12)nA sub n is equal to 20 times open paren negative 1 half close paren to the n th power

d)an=20⋅(−12)n−1

The table shows the distances travelled by a paper aeroplane. a. find the range and interquartile range of the data. the range is feet. the interquartile range is __feet. b. interpret the range and interquartile range of the data. __ feet the distances travelled by the paper aeroplane varied by no more than__ feet. the middle half of the distances travelled by the paper aeroplane varied by no more than __ feet.