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Solving And Graphing Inequalities

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Catatan pelajaran

Representing Inequalities as Regions

  • A 2D inequality (e.g. y < x, x + y ≥ 8) has a solution region in the xy-plane.
  • To draw the boundary line, replace the inequality sign with '=' and draw that line.
  • Use a solid line for ≤ or ≥ (line included); use a dotted line for < or > (line not included).
  • For y ≤ ... or y < ..., the wanted region is below the line; for y ≥ ... or y > ..., it is above.
  • For vertical lines: x < k → left of x = k; x > k → right of x = k.
  • If unsure, test a point (e.g. (0,0)) to see which side satisfies the inequality.
  • Shade the unwanted sides of each line to leave the wanted region clear; label it R.

Representing a system of inequalities as a shaded region

Representing a system of inequalities as a shaded region

Finding Inequalities from Regions

  • Identify the equation of each boundary line (use y = mx + c or x = k, y = k).
  • Note whether the line is solid (≤ or ≥) or dotted (< or >).
  • If the shaded region is below the line, use ≤ or <; if above, use ≥ or >.
  • For vertical lines: region left of x = k≤ or <; right≥ or >.
  • Test a point from the shaded region to confirm the inequality sign.
  • Write all inequalities together as the final answer.

Finding the inequalities that define a shaded region

Finding the inequalities that define a shaded region

Solving Linear Inequalities

  • Solve inequalities similarly to equations, but reverse the inequality sign when multiplying/dividing by a negative number.
  • Example: 3x + 12 < 5x - 3 → subtract 3x: 12 < 2x - 3 → add 3: 15 < 2xx > 7.5.
  • Example: 3n - 5 > 17 + 8n → subtract 3n: -5 > 17 + 5n → subtract 17: -22 > 5nn < -4.4.
  • Always check your solution by substituting a value back into the original inequality.

Shading Unwanted Regions (Exam Technique)

  • Read carefully: the question may ask you to shade unwanted regions or the wanted region.
  • Shading unwanted regions leaves the wanted region unshaded (clear).
  • Draw all boundary lines first, then shade each unwanted side.
  • Label the final wanted region with the letter R.
  • Use a test point (e.g. (0,0)) to decide which side to shade for each inequality.

Integer Solutions in a Region

  • Sometimes you need to find integer coordinates (x, y) inside a region that satisfy an additional equation.
  • List all integer points inside the region and check which satisfy the given equation.
  • Example: find (x, y) with integer coordinates inside R such that 3x + 5y = 35.

Word Problems: Forming Inequalities

  • Translate conditions into inequalities: 'fewer than 10 mats' → y < 10; 'at least 15 silver balloons' → x ≥ 15.
  • 'More gold than silver' → y > x; 'total no more than 70' → x + y ≤ 70.
  • For time constraints: e.g. 2.25 hours per basket and 1.5 hours per mat, max 22.5 hours → 2.25x + 1.5y ≤ 22.5 → multiply by 4: 9x + 6y ≤ 90 → divide by 3: 3x + 2y ≤ 30.
  • Always define variables clearly (e.g. x = number of baskets, y = number of mats).

Graphing Multiple Inequalities

  • Draw all boundary lines on the same axes using correct line styles (solid/dotted).
  • Shade the unwanted region for each inequality; the remaining unshaded area is the solution region.
  • Label the solution region R.
  • Check that a point inside R satisfies all inequalities.

Slide

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Soal latihan

Pratinjau gratis — 8 dari 51 soal. Daftar untuk melihat semuanya.
  1. 1.Which inequality represents the region below the line y = 3x + 2, including the line?

    Easy
    • Ay ≤ 3x + 2
    • By < 3x + 2
    • Cy ≥ 3x + 2
    • Dy > 3x + 2
  2. 2.Which line would be drawn as a dotted line when graphing the inequality y > 2x - 1?

    Easy
    • Ay = 2x - 1
    • By = 2x + 1
    • Cy = -2x - 1
    • Dy = -2x + 1
  3. 3.The inequality x ≥ 3 is represented on a graph by a vertical line at x = 3. Which side is the wanted region?

    Easy
    • ATo the right of the line
    • BTo the left of the line
    • CAbove the line
    • DBelow the line
  4. 4.Solve the inequality 3x + 12 < 5x - 3.

    Medium
    • Ax > 7.5
    • Bx < 7.5
    • Cx > 3
    • Dx < 3
  5. 5.Solve the inequality 3n - 5 > 17 + 8n.

    Medium
    • An < -4.4
    • Bn > -4.4
    • Cn < 4.4
    • Dn > 4.4
  6. 6.Solve the inequality x/2 - 13 > 12 + 3x.

    Medium
    • Ax < -10
    • Bx > -10
    • Cx < 10
    • Dx > 10
  7. 7.Which inequality is represented by the solid line y = 2x + 3 and the region above it?

    Easy
    • Ay ≥ 2x + 3
    • By > 2x + 3
    • Cy ≤ 2x + 3
    • Dy < 2x + 3
  8. 8.A region is defined by y ≤ 2, x ≥ 1, and y ≥ x. Which point lies inside the region?

    Medium
    • A(2, 2)
    • B(0, 0)
    • C(3, 4)
    • D(1, 3)

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