if f(x)=x^2-1 and g(x)=2x-3, what is the domain of (f*g)(x)

A:(negative infinity,positive infinity)
B: [-1,positive infinity)
C:[-5,positive infinity)
D:(positive infinity,negative infinity)

Question

if f(x)=x^2-1 and g(x)=2x-3, what is the domain of (f*g)(x)

A:(negative infinity,positive infinity)
B: [-1,positive infinity)
C:[-5,positive infinity)
D:(positive infinity,negative infinity)

astrophysics · Answer

Is it $$(f \circ g)(x)?$$

prupel85 · Answer

yeah

astrophysics · Answer

Ok that's the same thing as $$f(g(x))$$ meaning you can plug in the function g(x) wherever there exists an x in f(x)

astrophysics · Answer

Can you try that and see what you get

prupel85 · Answer

4x^2-10

astrophysics · Answer

$$f(g(x)) = \color\red{(2x-3)}^2-1$$ the red is g(x) and black is f(x)

astrophysics · Answer

Do you see how I did that?

prupel85 · Answer

yea i see  do i graph it next?

astrophysics · Answer

You could if you like, but we can do it algebraically, do you know how to find the domain for polynomials?

prupel85 · Answer

no i usually graph it and try to find the solutions

astrophysics · Answer

Well since it's a polynomial only the domain will be all real numbers

zzr0ck3r · Answer

hard to graph without the domain....

prupel85 · Answer

so its positive infinity to negative infinity

astrophysics · Answer

We write it as $$(- \infty, \infty)$$

astrophysics · Answer

Think of a number line |dw:1470378191042:dw|

prupel85 · Answer

okay