Math Problem Statement

A system of inequalities is shown below:

y<−2x+1y<−2x+1

x+2y≥−4x+2y≥−4

Which of the following is in the solution set of this system of inequalities?

A.(−9,1)(−9,1)

B.(−5,4)(−5,4)

C.(2,−3)(2,−3)

D.(6,−8)(6,−8)

Solution

To determine which point lies within the solution set of this system of inequalities, we’ll evaluate each of the given points for both inequalities in the system:

System of inequalities:

  1. y<2x+1y < -2x + 1
  2. x+2y4x + 2y \geq -4

Testing each option:

Option A: (9,1)(-9, 1)

  1. Substitute (9,1)(-9, 1) into the first inequality: y<2x+11<2(9)+11<18+11<19(True)y < -2x + 1 \Rightarrow 1 < -2(-9) + 1 \Rightarrow 1 < 18 + 1 \Rightarrow 1 < 19 \quad (\text{True})
  2. Substitute (9,1)(-9, 1) into the second inequality: x+2y49+2(1)49+2474(False)x + 2y \geq -4 \Rightarrow -9 + 2(1) \geq -4 \Rightarrow -9 + 2 \geq -4 \Rightarrow -7 \geq -4 \quad (\text{False})

Since the second inequality fails, Option A is not in the solution set.


Option B: (5,4)(-5, 4)

  1. Substitute (5,4)(-5, 4) into the first inequality: y<2x+14<2(5)+14<10+14<11(True)y < -2x + 1 \Rightarrow 4 < -2(-5) + 1 \Rightarrow 4 < 10 + 1 \Rightarrow 4 < 11 \quad (\text{True})
  2. Substitute (5,4)(-5, 4) into the second inequality: x+2y45+2(4)45+8434(True)x + 2y \geq -4 \Rightarrow -5 + 2(4) \geq -4 \Rightarrow -5 + 8 \geq -4 \Rightarrow 3 \geq -4 \quad (\text{True})

Since both inequalities are satisfied, Option B is in the solution set.


Option C: (2,3)(2, -3)

  1. Substitute (2,3)(2, -3) into the first inequality: y<2x+13<2(2)+13<4+13<3(False)y < -2x + 1 \Rightarrow -3 < -2(2) + 1 \Rightarrow -3 < -4 + 1 \Rightarrow -3 < -3 \quad (\text{False})

Since the first inequality fails, Option C is not in the solution set.


Option D: (6,8)(6, -8)

  1. Substitute (6,8)(6, -8) into the first inequality: y<2x+18<2(6)+18<12+18<11(False)y < -2x + 1 \Rightarrow -8 < -2(6) + 1 \Rightarrow -8 < -12 + 1 \Rightarrow -8 < -11 \quad (\text{False})

Since the first inequality fails, Option D is not in the solution set.


Conclusion:

The only point that satisfies both inequalities is Option B: (5,4)(-5, 4).


Would you like more details on how each inequality was solved, or do you have any questions?


  1. How can we solve a system of linear inequalities graphically?
  2. What methods can verify a point's inclusion in multiple inequalities?
  3. Why does the combination of “<” and “≥” limit solution sets for inequalities?
  4. How does changing inequality direction affect solution boundaries?
  5. What strategies help quickly determine valid points in a solution set?

Tip: Always check each inequality separately to verify all conditions for a solution point.

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Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Inequalities
Coordinate Plane

Formulas

Substitute values into y < −2x + 1
Substitute values into x + 2y ≥ −4

Theorems

Inequality properties
Coordinate point testing in inequalities

Suitable Grade Level

Grades 8-10