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Mathematics 8 Online
OpenStudy (anonymous):

Given that f(x) = −x + 4 and g(x) = −2x − 3, solve for f(g(x)) when x = 2.

OpenStudy (mathmale):

f(g(x)) is a "composite function." Can you define what that means? Once you understand this concept, the actual algebra and arithmetic are relatively simple.

OpenStudy (anonymous):

I don't really remember but know it

OpenStudy (mathmale):

Could you possibly look it up? And then write it down, for later reference and practice?

OpenStudy (anonymous):

yes

OpenStudy (mathmale):

So, what have you learned by looking up "composite function" ?

OpenStudy (anonymous):

x is a placeholder and there's domain and range.

OpenStudy (mathmale):

I see that g(x) is the INPUT to function f(x), in f(g(x)). Write out f(x). Replace every instance of x with empty parentheses: f( ) = -( ) + 4 Write function g(x) = -2x -3 inside those empty parentheses: g(x) in the left set of empty parentheses, -2x-3 in the right set. Simplify the resulting expression.

OpenStudy (anonymous):

f(x)=-2(3)+4

OpenStudy (mathmale):

f( ) = -( ) + 4 has 2 sets of empty parentheses. Write g(x) inside the left set and write -2x-3 inside the other set. This will give you an expression for the composite function f(g(x)). Simplify the right side.

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