Algebra · real student question

Solve the inequality 25 - 2(n - 2) >= -8n + 6.

Question

Solve the inequality

252(n2)8n+625-2(n-2)\ge -8n+6

Step-by-step solution

  1. Distribute the -2 across the parentheses. The minus sign belongs to the 22, so both inner terms change: 2n=2n-2\cdot n=-2n and 2(2)=+4-2\cdot(-2)=+4. Dropping that sign flip on the second term is the classic mistake here.

    252n+48n+625-2n+4\ge -8n+6

  2. Combine the constants on the left. 25+4=2925+4=29, giving

    292n8n+629-2n\ge -8n+6

  3. Move the n terms to one side by adding 8n. Adding the same quantity to both sides never changes the direction of an inequality, and adding 8n8n (rather than subtracting 2n2n) keeps the coefficient positive, which avoids a later flip:

    29+6n629+6n\ge 6

  4. Isolate the n term. Subtract 2929 from both sides:

    6n236n\ge -23

  5. Divide by 6 and explain why the sign holds. Because 6>06>0, dividing preserves \ge:

    n236n\ge -\frac{23}{6}

    The fraction does not reduce, since 2323 is prime and does not divide 66. As a decimal, 2363.83-\tfrac{23}{6}\approx-3.8\overline{3}.

  6. Check the boundary and one interior point. At n=236n=-\tfrac{23}{6}: left =252(2362)=25+706=2206=25-2\left(-\tfrac{23}{6}-2\right)=25+\tfrac{70}{6}=\tfrac{220}{6} and right =8(236)+6=1846+366=2206=-8\left(-\tfrac{23}{6}\right)+6=\tfrac{184}{6}+\tfrac{36}{6}=\tfrac{220}{6} — equal, as expected at the boundary ✓. At n=0n=0 (inside the solution set): 252(2)=29625-2(-2)=29\ge 6 ✓, so the inequality really does point the way stated.

Answer

n236n\ge -\frac{23}{6}

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