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Given the definitions of 
f(x) and 
g(x) below, find the value of 
(g@f)(-2).

{:[f(x)=-x-5],[g(x)=2x^(2)+4x-6]:}
Answer:

Given the definitions of f(x) f(x) and g(x) g(x) below, find the value of (gf)(2) (g \circ f)(-2) .\newlinef(x)=x5g(x)=2x2+4x6 \begin{array}{l} f(x)=-x-5 \\ g(x)=2 x^{2}+4 x-6 \end{array} \newlineAnswer:

Full solution

Q. Given the definitions of f(x) f(x) and g(x) g(x) below, find the value of (gf)(2) (g \circ f)(-2) .\newlinef(x)=x5g(x)=2x2+4x6 \begin{array}{l} f(x)=-x-5 \\ g(x)=2 x^{2}+4 x-6 \end{array} \newlineAnswer:
  1. Understand composition of functions: Understand the composition of functions. The composition of functions gf)(x) meanswefirstapply$fg\circ f)(x)\ means we first apply \$f to xx, and then apply gg to the result of f(x)f(x). In notation, this is g(f(x))g(f(x)).
  2. Calculate f(2)f(-2): Calculate f(2)f(-2). We have f(x)=x5f(x) = -x - 5. To find f(2)f(-2), we substitute xx with 2-2. f(2)=(2)5=25=3f(-2) = -(-2) - 5 = 2 - 5 = -3.
  3. Calculate g(f(2))g(f(-2)): Calculate g(f(2))g(f(-2)).\newlineNow that we have f(2)=3f(-2) = -3, we need to find g(3)g(-3). The function g(x)g(x) is given by g(x)=2x2+4x6g(x) = 2x^2 + 4x - 6.\newlineSubstitute xx with 3-3 into g(x)g(x).\newlineg(3)=2(3)2+4(3)6g(-3) = 2(-3)^2 + 4(-3) - 6.
  4. Simplify g(3)g(-3): Simplify g(3)g(-3).\newlineCalculate the value of g(3)g(-3) step by step.\newlineg(3)=2(9)+4(3)6g(-3) = 2(9) + 4(-3) - 6\newlineg(3)=18126g(-3) = 18 - 12 - 6\newlineg(3)=66g(-3) = 6 - 6\newlineg(3)=0g(-3) = 0.

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