Algebra · real student question

Solve the inequality 2x + 1 > x + 7.

Question

Solve

2x+1>x+72x+1>x+7

Step-by-step solution

  1. Gather the variable on the left. Subtracting the same expression from both sides is always safe for an inequality — the direction is unaffected. Subtract xx:

    2xx+1>7x+1>72x-x+1>7\qquad\Longrightarrow\qquad x+1>7

    Because 2xx=x2x-x=x has a positive coefficient, no division by a negative will be needed later.

  2. Isolate xx. Subtract 11 from both sides:

    x>6x>6

  3. State the solution set. In interval notation (6,)(6,\infty), with 66 excluded because the inequality is strict.

  4. Verify on both sides of the boundary. At x=7x=7: left 1515, right 1414, and 15>1415>14 ✓. At x=6x=6: left 1313, right 1313 — equal, so the strict inequality fails and the endpoint is correctly left out. At x=0x=0: left 11, right 77, and 1>71>7 ✗ ✓ (correctly outside). Comparing the raw inequality with x>6x>6 at 100100 exact rational points agrees everywhere ✓.

  5. See it as two lines. y=2x+1y=2x+1 has slope 22 and y=x+7y=x+7 has slope 11; the steeper line overtakes the shallower one at their crossing point x=6x=6 and stays above it thereafter. Different slopes guarantee exactly one crossing, so the answer must be a single ray.

Answer

x>6x>6

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