A particular strain of bacterium has 20 bacteria in generation 1 and triples in population every generation. The explicit formula for the number of bacteria
in generation n is:
a(n) = 20-3(n-1)
How many bacteria are in generation 9?
A. 480
B. 131,220
C. 6561
D. 393,660

Which of the following circles have their centers on the x-axis? check all that apply.

Ineed here’s a picture of the question

Grace is standing 18 feet from a lighthouse and kelly is standing 10 feet from grace. the angle that grace looks up to see the top of the lighthouse is 45°. the angle that kelly looks up to see the top of the lighthouse is y°. find the height, h, of the lighthouse. find the angle, rounded to the nearest tenth of a degree, in which kelly looks up to the top of the lighthouse. to the nearest tenth of a degree, find the value of x° . in two or more sentences, explain your calculations