Math Problem Statement

By plotting the lines 2x - y = 3, y = -x, and y = 7 on a grid, find the area of the region enclosed between the three lines. Give your answer in square units.

Solution

Let's analyze the problem by finding the equations of the lines and solving the region enclosed by them:

Step 1: Equations of the Lines

The equations given are:

  1. 2xy=32x - y = 3, which we can rewrite as: y=2x3y = 2x - 3
  2. y=xy = -x
  3. y=7y = 7

Step 2: Find the Points of Intersection

We need to find the points of intersection of the three lines to define the vertices of the region enclosed.

  • Intersection of y=2x3y = 2x - 3 and y=xy = -x: 2x3=x2x - 3 = -x Solving for xx: 3x=3    x=13x = 3 \implies x = 1 Substituting x=1x = 1 into y=xy = -x: y=1y = -1 So, the intersection point is (1,1)(1, -1).

  • Intersection of y=2x3y = 2x - 3 and y=7y = 7: 7=2x37 = 2x - 3 Solving for xx: 2x=10    x=52x = 10 \implies x = 5 So, the intersection point is (5,7)(5, 7).

  • Intersection of y=xy = -x and y=7y = 7: 7=x7 = -x Solving for xx: x=7x = -7 So, the intersection point is (7,7)(-7, 7).

Step 3: Vertices of the Triangle

The vertices of the triangle formed by the three lines are:

  1. (1,1)(1, -1)
  2. (5,7)(5, 7)
  3. (7,7)(-7, 7)

Step 4: Calculate the Area

We can use the formula for the area of a triangle given its vertices (x1,y1),(x2,y2),(x3,y3)(x_1, y_1), (x_2, y_2), (x_3, y_3): Area=12x1(y2y3)+x2(y3y1)+x3(y1y2)\text{Area} = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right|

Substitute the coordinates (1,1),(5,7),(7,7)(1, -1), (5, 7), (-7, 7): Area=121(77)+5(7(1))+(7)(17)\text{Area} = \frac{1}{2} \left| 1(7 - 7) + 5(7 - (-1)) + (-7)(-1 - 7) \right| =121(0)+5(8)+(7)(8)= \frac{1}{2} \left| 1(0) + 5(8) + (-7)(-8) \right| =120+40+56=12×96=48= \frac{1}{2} \left| 0 + 40 + 56 \right| = \frac{1}{2} \times 96 = 48

So, the area of the enclosed region is 48 square units.

Would you like further details or explanations on any step?

Here are 5 related questions to consider:

  1. How do you find the intersection points of two lines algebraically?
  2. What other methods can you use to find the area of a triangle given its vertices?
  3. How would the process change if one of the equations were a curve, like y=x2y = x^2?
  4. Can you use a geometric approach to estimate the area of this triangle without algebra?
  5. How would graphing the equations help visualize the solution?

Tip: Always double-check the intersection points, as they form the basis for calculating the enclosed region's area.

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Intersection of Lines
Area of a Triangle

Formulas

Equation of a line y = mx + c
Area of a triangle given vertices: (1/2) * |x1(y2 - y3) + x2(y3 - y1) + x3(y1 - y2)|

Theorems

Basic properties of linear equations
Determinant formula for the area of a triangle

Suitable Grade Level

Grades 8-10