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📐 Mathematics  ·  Linear Inequalities  ·  JEE

Find all x such that (x-1)(x-2) >= 0 using the sign-rule method for inequalities (not just linear, as an extension exercise).

Answer: x = 2.

  • A x <= 1 or x >= 2
  • B 1 <= x <= 2
  • C x < 1 or x > 2 only
  • D No solution

Correct answer: A. x <= 1 or x >= 2

Explanation: Sign-rule method: critical points x=1 and x=2 divide the number line into three intervals. Test each: x<1: (-)(-) =+≥0 ✓; 1&lt;x&lt;2: (+)(-) =-<0 ✗; x>2: (+)(+)=+≥0 ✓. Include endpoints (equality holds). Answer: x ≤ 1 or x ≥ 2

Number Line vs Half-Plane Representationx > 2 (open circle, hollow)2x ≤ 2 (closed circle, filled)shaded regionsatisfies the inequality2D inequality: dashed line = strict, shaded = solution side

One-variable inequalities use open (excluded) or closed (included) circles on a number line; two-variable inequalities use a dashed (strict) or solid (non-strict) boundary line, with the solution being the entire shaded half-plane on one side of it.

Concept context

Solving linear inequalities in one and two variables algebraically and graphically, and representing solutions on a number line or as a region in a plane.

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