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Given functions f(x) = 2x + 7 and g(x) = 3/(x-2), find f⁻¹(x), gf(x), and gf(-2).

Mathematics

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Answers

3 parts
a

f−1(x)=x−72f^{-1}(x) = \frac{x - 7}{2}

b

gf(x)=32x+5gf(x) = \frac{3}{2x + 5}

c
3

Step-by-step solution

10 steps

Here are the solutions for the given functions:

Given functions:

f(x)=2x+7f(x) = 2x + 7 g(x)=3x−2g(x) = \frac{3}{x-2}

Part a· 4 steps

Find f−1(x)f^{-1}(x)

  1. Set y=f(x)y = f(x).

    y=2x+7y = 2x + 7
  2. Swap xx and yy.

    x=2y+7x = 2y + 7
  3. Solve for yy.

    Subtract 7 from both sides:

    x−7=2yx - 7 = 2y

    Divide by 2:

    y=x−72y = \frac{x - 7}{2}
  4. Replace yy with f−1(x)f^{-1}(x).

    f−1(x)=x−72f^{-1}(x) = \frac{x - 7}{2}

    The inverse function is f−1(x)=x−72\boxed{f^{-1}(x) = \frac{x - 7}{2}}.

Part b

gf(x)=32x+5gf(x) = \frac{3}{2x + 5}

Find gf(x)gf(x)

  1. Substitute f(x)f(x) into g(x)g(x).

    The definition of gf(x)gf(x) is g(f(x))g(f(x)).
    Replace xx in g(x)g(x) with f(x)f(x).

    gf(x)=g(2x+7)gf(x) = g(2x + 7)
  2. Apply the definition of g(x)g(x).

    gf(x)=3(2x+7)−2gf(x) = \frac{3}{(2x + 7) - 2}
  3. Simplify the expression.

    gf(x)=32x+5gf(x) = \frac{3}{2x + 5}

    The composite function is gf(x)=32x+5\boxed{gf(x) = \frac{3}{2x + 5}}.

Part c3

Find gf(−2)gf(-2)

  1. Use the expression for gf(x)gf(x) found in part b.

    gf(x)=32x+5gf(x) = \frac{3}{2x + 5}
  2. Substitute x=−2x = -2 into the expression.

    gf(−2)=32(−2)+5gf(-2) = \frac{3}{2(-2) + 5}
  3. Simplify the denominator.

    gf(−2)=3−4+5gf(-2) = \frac{3}{-4 + 5} gf(−2)=31gf(-2) = \frac{3}{1} gf(−2)=3gf(-2) = 3

    The value of gf(−2)gf(-2) is 3\boxed{3}.

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