A function has a constant doubling time. What type of function does this
represent?

  an exponential function

Step-by-step explanation:

An exponential function has the characteristic that it increases by a constant factor when the independent variable increases by a constant increment. The function you describe is an exponential function.

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It can be written in the form ...

  f(t) = f(0)·2^(t/d) . . . . . where d is the doubling time

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this

b.-4 units

all you   do is count how many times you move