Algebra · real student question

Solve the inequality 7|w - 6| >= 2.

Question

Solve the inequality

7w627|w-6|\ge2

Step-by-step solution

  1. Isolate the absolute value before splitting anything. The rewrite rules for A|A| only apply when the absolute value stands alone. Here it is multiplied by 77, so divide both sides by the positive number 77 (no sign flip):

    w627|w-6|\ge\frac{2}{7}

  2. Split a greater-than-or-equal absolute value into two rays. Ab|A|\ge b with b>0b>0 says the distance from AA to 00 is at least bb, which happens on the two sides away from the origin — not between them:

    w627orw627w-6\le-\frac{2}{7}\qquad\text{or}\qquad w-6\ge\frac{2}{7}

    The word is or, never and: no single ww can be both far left and far right at once.

  3. Solve each branch by adding 6. Convert 66 to sevenths so the fractions combine cleanly, 6=4276=\tfrac{42}{7}:

    w42727=407orw427+27=447w\le\frac{42}{7}-\frac{2}{7}=\frac{40}{7}\qquad\text{or}\qquad w\ge\frac{42}{7}+\frac{2}{7}=\frac{44}{7}

  4. Write the solution set. In interval notation

    (,407][447,)\left(-\infty,\tfrac{40}{7}\right]\cup\left[\tfrac{44}{7},\infty\right)

    Both endpoints are included because the original relation allowed equality. Numerically the excluded gap is the short open interval (5.714,6.285)(5.714\ldots,\,6.285\ldots) centred on w=6w=6.

  5. Verify the boundary and the gap. At w=407w=\tfrac{40}{7}: 74076=727=227\left|\tfrac{40}{7}-6\right|=7\cdot\tfrac{2}{7}=2\ge2 ✓ (equality, so the endpoint belongs). At the centre w=6w=6: 70=07|0|=0, which is not 2\ge2 ✗, confirming the gap. Comparing the raw inequality with the claimed set at 500500 exact rational points agrees everywhere ✓.

Answer

w407orw447w\le\frac{40}{7}\quad\text{or}\quad w\ge\frac{44}{7}

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