Rational Inequality...2

Discussion in 'Other Pre-University Math' started by nycmathguy, Oct 3, 2021.

  1. nycmathguy

    nycmathguy

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    Section 2.7
    Question 44

    20210930_232249.jpg
    (x + 12)/(x + 2) ≥ 3

    Simplifying the rational inequality just a bit, I get

    (-2x + 6)/(x + 2) ≥ 0

    Set denominator to zero and solve for x.

    I get x = -2. This means x cannot be -2 here.
    If x = -2, we get division by zero which is undefined.

    Now, solving -2x + 6)/(x + 2) ≥ 0 for x, I get the following: x ≤ 3.

    Plot x = -2 and x = 3 on the real number line and test each interval.

    <-------(-2)---------(3)--------->

    When x = -3, we get a false statement.
    As stated above, x cannot be -2.
    When x = 0, we get a true statement.
    When x = 3, we get a true statement.
    When x = 4, we get a false statement.

    The only solution interval I see is [0,3].

    Here it is on the real number line:

    20211002_205051.jpg

    You say?
     
    nycmathguy, Oct 3, 2021
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  2. nycmathguy

    MathLover1

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    x cannot be -2, true, but x can be greater than -2
    solution is:
    -2<x<=3

    (-2, 3]

    upload_2021-10-2_20-8-7.png
     
    MathLover1, Oct 3, 2021
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  3. nycmathguy

    nycmathguy

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    Can you break it down step by step? How did you end up with (-2, 3]?

    While you show me how this is done, I will also watch a few video lessons. I need to solve at least 3 more rational inequality problems from the current section. I cannot go beyond Section 2.7 without knowing this very important precalculus topic. I need to feel confident with rational inequality. Otherwise, I stop right here.

    P. S. Look for some Calculus 1 questions tonight.
     
    nycmathguy, Oct 3, 2021
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  4. nycmathguy

    MathLover1

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    (-2x + 6)/(x + 2) ≥ 0
    if (-2x + 6) ≥ 0 => x<=3

    if denominator (x + 2) ≥ 0 => x>=-2 ; since denominator cannot be = to 0, we use only x>-2

    combine solutions: -2<x<=3
     
    MathLover1, Oct 3, 2021
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  5. nycmathguy

    nycmathguy

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    Thank you. I will do 46, 48, 50 and 52 for additional practice BUT only after watching a few video clips.
     
    nycmathguy, Oct 3, 2021
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