Function help

Question

Compose A(x)=pi•x^2 with r(x)=.5x. Find A(r(5))

Answer 1

The key to success is to attack this problem in proper order:

 

1.  substitute 5 in for r:

 

r(5)=.5(.5) = .25

 

Note this is r(x) when x is equal to 5.

 

Now solve A(x) substitute .25 for r(5):

 

a(r(5)= pi*(.25)^2 = 0.0625*pi (also can be expressed (1/16)*pi)

 

Tim