Algebra · real student question

Solve the inequality 4 - 2m - m + 3 > 0.

Question

Solve

42mm+3>04-2m-m+3>0

Step-by-step solution

  1. Sort the four terms into two groups. The constants are 44 and +3+3; the variable terms are 2m-2m and m-m. Grouping like with like:

    4+3=7,2mm=3m4+3=7,\qquad -2m-m=-3m

  2. Rewrite the simplified inequality.

    73m>07-3m>0

  3. Add 3m3m to both sides instead of dividing by a negative. This keeps the variable coefficient positive and removes any need for a sign flip:

    7>3m7>3m

  4. Divide by 33 and rewrite with mm first.

    73>mm<73\frac{7}{3}>m\quad\Longleftrightarrow\quad m<\frac{7}{3}

  5. Confirm with test values. At m=0m=0: 400+3=7>04-0-0+3=7>0 \checkmark. At m=3m=3: 463+3=204-6-3+3=-2\not>0 \checkmark. At m=73m=\tfrac73: 7373=07-3\cdot\tfrac73=0, which is not >0>0, so the boundary is correctly excluded.

Answer

m<73,i.e. (,73)m<\frac{7}{3},\qquad\text{i.e. }\left(-\infty,\tfrac{7}{3}\right)

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