Algebra · real student question

Solve the inequality x - 4 > 11.

Question

Solve

x4>11x-4>11

Step-by-step solution

  1. Choose the inverse operation. The variable has 44 subtracted from it, so adding 44 isolates it. Adding the same number to both sides preserves the inequality's direction — only multiplying or dividing by a negative would flip it, and that never happens here.

  2. Add 4 to both sides.

    x4+4>11+4x>15x-4+4>11+4\qquad\Longrightarrow\qquad x>15

  3. State the solution set. In interval notation (15,)(15,\infty), with 1515 excluded because the relation is strict.

  4. Verify around the boundary. At x=16x=16: 164=1216-4=12, and 12>1112>11 ✓ (inside). At x=15x=15: 154=1115-4=11, and 11>1111>11 is false, so the endpoint is correctly open ✓. At x=12x=12: 8>118>11 ✗ (outside). The raw inequality and x>15x>15 agree at 5050 exact rational points ✓.

  5. Note the shortcut. For xc>dx-c>d the answer is always x>c+dx>c+d; here 4+11=154+11=15 ✓. Recognising the pattern turns the problem into a single addition, and it doubles as a check on the algebra.

Answer

x>15x>15

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