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Given that f(t) = 1 − (3)/(t) and the range is \-1, 3, 7\, find the domain.

Mathematics

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3 parts
b

(−∞,1](-\infty,1]

c

f(x)≥−1f(x)\ge-1

d

(ab)n=1\left( \frac{a}{b} \right)^{n} = 1

Graph of f(t) = 1 − 3/t

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Key points of f(t) = 1 − 3/t
Pointty
x-intercept30

Step-by-step solution

7 steps

Part b· 4 steps

To find the domain DD such that the range of f(x)=1x−2f(x) = \frac{1}{x-2} is [−1,0)[-1, 0).

  1. Solve y=1x−2y = \frac{1}{x-2} for xx.

    y=1x−2y = \frac{1}{x-2} x−2=1yx - 2 = \frac{1}{y} x=2+1y,y≠0x = 2 + \frac{1}{y}, \quad y \neq 0
  2. f′(x)=−1(x−2)2<0f'(x) = -\frac{1}{(x-2)^2} < 0, so ff is strictly decreasing on (−∞,2)(-\infty, 2) and on (2,∞)(2, \infty).

    On (−∞,2)(-\infty, 2), f(x)<0f(x) < 0: as x→−∞x \to -\infty, f(x)→0−f(x) \to 0^-; as x→2−x \to 2^-, f(x)→−∞f(x) \to -\infty.

  3. Solve f(x)=−1f(x) = -1.

    1x−2=−1\frac{1}{x-2} = -1 x−2=−1x-2 = -1 x=1x = 1

    f(1)=−1f(1) = -1.

  4. Since ff is strictly decreasing on (−∞,2)(-\infty, 2), on (−∞,1](-\infty, 1], ff decreases from 0−0^- to −1-1.

    Thus, f((−∞,1])=[−1,0)f((-\infty, 1]) = [-1, 0).

    Domain: (−∞,1](-\infty, 1]
    (-\infty,1]

Part c

f(x)≥−1f(x)\ge-1

f(x)=x2−2xf(x) = x^2 - 2x. Show f(x)≥−1f(x) \ge -1 for all real xx.

  1. Complete the square.

    f(x)=x2−2x=(x2−2x+1)−1=(x−1)2−1f(x) = x^2 - 2x = (x^2 - 2x + 1) - 1 = (x-1)^2 - 1
  2. (x−1)2≥0(x-1)^2 \ge 0 for all real xx.

    f(x)=(x−1)2−1≥0−1=−1f(x) = (x-1)^2 - 1 \ge 0 - 1 = -1

    Equality at x=1x=1: f(1)=−1f(1) = -1.

    Alternatively, f′(x)=2x−2=0f'(x) = 2x - 2 = 0 gives x=1x=1, f′′(x)=2>0f''(x)=2>0 so minimum f(1)=−1f(1)=-1.

    Thus, f(x)≥−1f(x) \ge -1 for all xx.

    f(x)\ge-1

Part d

(ab)n=1\left( \frac{a}{b} \right)^{n} = 1

Given an=bna^n = b^n, show (ab)n=1\left( \frac{a}{b} \right)^n = 1 (assume b≠0b \neq 0).

  1. Divide both sides by bnb^n.

    an=bna^n = b^n anbn=bnbn\frac{a^n}{b^n} = \frac{b^n}{b^n} (ab)n=1\left( \frac{a}{b} \right)^n = 1

    If b=0b=0, then an=0a^n=0 so a=0a=0, but ab\frac{a}{b} undefined.

    **\left( \frac{a}{b} \right)^{n} = 1}

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