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The function 
f is given by 
f(x)=x^(2)+1, and the function 
g is given by 
g(x)=((x-3))/(x). Which of the following is an expression for 
f(g(x)) ?
(A) 
(x^(3)-3x^(2)+x-3)/(x)
(B) 
(x^(2)-2)/(x^(2)+1)
(C) 
(x^(2)-6x+9)/(x^(2))+1
(D) 
(x^(2)-8)/(x^(2))

The function f f is given by f(x)=x2+1 f(x)=x^{2}+1 , and the function g g is given by g(x)=(x3)x g(x)=\frac{(x-3)}{x} . Which of the following is an expression for f(g(x)) f(g(x)) ?\newline(A) x33x2+x3x \frac{x^{3}-3 x^{2}+x-3}{x} \newline(B) x22x2+1 \frac{x^{2}-2}{x^{2}+1} \newline(C) x26x+9x2+1 \frac{x^{2}-6 x+9}{x^{2}}+1 \newline(D) x28x2 \frac{x^{2}-8}{x^{2}}

Full solution

Q. The function f f is given by f(x)=x2+1 f(x)=x^{2}+1 , and the function g g is given by g(x)=(x3)x g(x)=\frac{(x-3)}{x} . Which of the following is an expression for f(g(x)) f(g(x)) ?\newline(A) x33x2+x3x \frac{x^{3}-3 x^{2}+x-3}{x} \newline(B) x22x2+1 \frac{x^{2}-2}{x^{2}+1} \newline(C) x26x+9x2+1 \frac{x^{2}-6 x+9}{x^{2}}+1 \newline(D) x28x2 \frac{x^{2}-8}{x^{2}}
  1. Substitute into f(x)f(x): First, we need to substitute the expression for g(x)g(x) into the function f(x)f(x).\newlinef(x)=x2+1f(x) = x^2 + 1\newlineg(x)=x3xg(x) = \frac{x - 3}{x}\newlineSo, f(g(x))=f(x3x)f(g(x)) = f\left(\frac{x - 3}{x}\right)
  2. Replace xx in f(x)f(x): Now we will replace every instance of xx in f(x)f(x) with (x3)/x(x - 3) / x.
    f(g(x))=((x3)/x)2+1f(g(x)) = ((x - 3) / x)^2 + 1
  3. Expand binomial square: Next, we will expand the square of the binomial (x3x)2\left(\frac{x - 3}{x}\right)^2.
    f(g(x))=((x3)2x2)+1f(g(x)) = \left(\frac{(x - 3)^2}{x^2}\right) + 1
    f(g(x))=(x26x+9x2)+1f(g(x)) = \left(\frac{x^2 - 6x + 9}{x^2}\right) + 1
  4. Combine terms: Now we will combine the terms over a common denominator.\newlinef(g(x))=x26x+9x2+x2x2f(g(x)) = \frac{x^2 - 6x + 9}{x^2} + \frac{x^2}{x^2}\newlinef(g(x))=x26x+9+x2x2f(g(x)) = \frac{x^2 - 6x + 9 + x^2}{x^2}
  5. Simplify numerator: We simplify the numerator by combining like terms. f(g(x))=2x26x+9x2f(g(x)) = \frac{2x^2 - 6x + 9}{x^2}
  6. Check for mistakes: We notice that the expression (2x26x+9)/x2(2x^2 - 6x + 9) / x^2 is not among the answer choices, so we must have made a mistake. Let's go back and check our work.

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