How do you graph #f(x)=(1/3)^x-3# by plotting points?

1 Answer
Jul 4, 2017

See below

Explanation:

#f(x) = (1/3)^x - 3#

Before we start plotting points, let's first get an idea of some of the characterics of #f(x)#

#lim_(x->+oo) f(x) = 0 -3 = -3#
We should note that #f(x) -> -3# very rapidly.
I.e. We wont need very many points #x>0#

#lim_(x->-oo) f(x) = lim_(x->+oo) 3^x-3 = +oo#
Again #f(-x) -> oo# quite rapidly.

#f(0) = (1/3)^0 -3 = 1-3 =-2#

So, #(0, -2)# is a point on our graph

#f(x) =0 -> (1/3)^x = 3#

#3^(-x) = 3^1 -> x=-1#

So, #(-1, 0)# is another point on our graph.

Calculating other points:

#f(1) = 1/3-3 approx -2.667#

#f(2) = 1/9-3 approx -2.889#

#f(3) = 1/27-3 approx -2.963#

#f(-2) = 9-3 =6#

#f(-3) = 27-3 =24#

We can use the chracteristics and calculated points of #f(x)# to plot a graph as produced below.

graph{(1/3)^x-3 [-7.9, 7.9, -3.935, 3.97]}