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Given the function f(y) = 1 − (3)/(y), find the domain of y for which the range of f(y) is in the interval (-2, 7).

Mathematics

ScanSolve AI Answer

Answer

b

(−∞,−12)∪(1,∞)\left(-\infty, -\frac{1}{2}\right) \cup (1, \infty)

Graph of f(y) = 1 − 3/y

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Key points of f(y) = 1 − 3/y
Pointyy
x-intercept30

Step-by-step solution

4 steps

Step 1: Understand the function and the given range.
The function is f(y)=1−3yf(y) = 1 - \frac{3}{y}.
The range is given as the interval (−2,7)(-2, 7), which means −2<f(y)<7-2 < f(y) < 7.
We need to find the values of yy (the domain) for which f(y)f(y) falls within this range.

Step 2: Set up inequalities based on the range.
We have two inequalities to solve:

Part a

f(y)>−2f(y) > -2

Part b

(−∞,−12)∪(1,∞)\left(-\infty, -\frac{1}{2}\right) \cup (1, \infty)

f(y)<7f(y) < 7

  1. Solve inequality a) for yy.

    1−3y>−21 - \frac{3}{y} > -2

    Add 2 to both sides:

    3−3y>03 - \frac{3}{y} > 0

    Multiply by yy (we must consider two cases for y>0y > 0 and y<0y < 0):
    Case 1: y>0y > 0

    3y−3>03y - 3 > 0 3y>33y > 3 y>1y > 1

    So, for y>0y > 0, the condition is y>1y > 1.

    Case 2: y<0y < 0
    When multiplying by a negative number, reverse the inequality sign:

    3y−3<03y - 3 < 0 3y<33y < 3 y<1y < 1

    So, for y<0y < 0, the condition is y<1y < 1. Since we assumed y<0y < 0, this means all y<0y < 0 satisfy the inequality.

    Combining both cases for f(y)>−2f(y) > -2, the solution is y<0y < 0 or y>1y > 1.
    In interval notation: (−∞,0)∪(1,∞)(-\infty, 0) \cup (1, \infty).

  2. Solve inequality b) for yy.

    1−3y<71 - \frac{3}{y} < 7

    Subtract 1 from both sides:

    −3y<6-\frac{3}{y} < 6

    Multiply by −1-1 and reverse the inequality sign:

    3y>−6\frac{3}{y} > -6

    Multiply by yy (again, consider two cases):
    Case 1: y>0y > 0

    3>−6y3 > -6y −36<y-\frac{3}{6} < y y>−12y > -\frac{1}{2}

    So, for y>0y > 0, the condition is y>−12y > -\frac{1}{2}. Since we assumed y>0y > 0, this means all y>0y > 0 satisfy the inequality.

    Case 2: y<0y < 0
    When multiplying by a negative number, reverse the inequality sign:

    3<−6y3 < -6y −36>y-\frac{3}{6} > y y<−12y < -\frac{1}{2}

    So, for y<0y < 0, the condition is y<−12y < -\frac{1}{2}.

    Combining both cases for f(y)<7f(y) < 7, the solution is y<−12y < -\frac{1}{2} or y>0y > 0.
    In interval notation: (−∞,−12)∪(0,∞)(-\infty, -\frac{1}{2}) \cup (0, \infty).

  3. Find the intersection of the solutions from Step 3 and Step 4.

    We need yy to satisfy both conditions:
    Condition 1: y∈(−∞,0)∪(1,∞)y \in (-\infty, 0) \cup (1, \infty)
    Condition 2: y∈(−∞,−12)∪(0,∞)y \in (-\infty, -\frac{1}{2}) \cup (0, \infty)

    Let's find the intersection of these two sets:
    The intersection of (−∞,0)(-\infty, 0) and (−∞,−12)(-\infty, -\frac{1}{2}) is (−∞,−12)(-\infty, -\frac{1}{2}).
    The intersection of (1,∞)(1, \infty) and (0,∞)(0, \infty) is (1,∞)(1, \infty).
    The other intersections are empty.

    Therefore, the domain for the given range is y<−12y < -\frac{1}{2} or y>1y > 1.
    In interval notation, the domain is (−∞,−12)∪(1,∞)\boxed{\left(-\infty, -\frac{1}{2}\right) \cup (1, \infty)}.

  4. Present the answer on an arrow diagram.

    An arrow diagram shows the mapping from the domain to the range.
    Domain: D={y∈R∣y<−12 or y>1}D = \left\{y \in \mathbb{R} \mid y < -\frac{1}{2} \text{ or } y > 1\right\}
    Range: R={f(y)∈R∣−2<f(y)<7}R = \{f(y) \in \mathbb{R} \mid -2 < f(y) < 7\}

    The arrow diagram can be represented as:

    Domain (−∞,−12)∪(1,∞)→f(y)=1−3yRange (−2,7)\text{Domain } \left(-\infty, -\frac{1}{2}\right) \cup (1, \infty) \quad \xrightarrow{f(y) = 1 - \frac{3}{y}} \quad \text{Range } (-2, 7)
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