Need help with computing functions

[MathFail]

Thanks in advance

 

[Steven G]

f(x) = 1-4x. This says to find f(x) you subtract 4*x from 1. Now matter what you put in f( ? ) you will get 1-4*? It does not matter what ? is! So f(a-bc) = 1 - 4(a-bc). The rule for f is 1 - 4* (what is in the parenthesis!)

Please try again and post back.

Also f = 1-4x and g= 3x+1 is NOT correct. It is f(x) = 1-4x and g(x) = 3x+1. At least I assume that is true. If could have been that f(2x) = 1-4x so f(x) = 1-2x

 

[Dr.Peterson]

Your third line is wrong. Your fourth line is actually g(f(x)), not f(g(x))! Your fifth line has an extraneous x.

The important thing here is to realize that f(something) means that you replace x in the definition of f with "something". So here, f(3x+1) means you replace x in 1-4x with f(x) = (3x+1), resulting in f(3x+1) = 1-4(3x+1). Do you see that?

 

[MathFail]

So would it be written as 1-4(3x+1)?

 

[MathFail]

So would it then be rewritten as: 1-4(3x+1) ?

Your third line is wrong. Your fourth line is actually g(f(x)), not f(g(x))! Your fifth line has an extraneous x.

The important thing here is to realize that f(something) means that you replace x in the definition of f with "something". So here, f(3x+1) means you replace x in 1-4x with f(x) = (3x+1), resulting in f(3x+1) = 1-4(3x+1). Do you see that?

 

[Dr.Peterson]

So would it then be rewritten as: 1-4(3x+1) ?

Yes.

Now just simplify it.