Math Problem Statement

The equations of four lines are given. Identify which lines are perpendicular. Line 1: y=2 Line 2: y=1/5x−3 Line 3: x=−4 Line 4: y+1=−5(x+2) Lines 2 and 4 are perpendicular. None of the lines are perpendicular. Lines 1 and 3 are perpendicular. Lines 1 and 3 are perpendicular, and Lines 2 and 4 are perpendicular.

Solution

To determine which lines are perpendicular, we need to look at their slopes. Two lines are perpendicular if the product of their slopes is 1-1.

Let's analyze the equations one by one.

Line 1: y=2y = 2

  • This is a horizontal line, and horizontal lines have a slope of 0.

Line 2: y=15x3y = \frac{1}{5}x - 3

  • This is in slope-intercept form, y=mx+by = mx + b, where mm is the slope. So, the slope of this line is 15\frac{1}{5}.

Line 3: x=4x = -4

  • This is a vertical line, and vertical lines have an undefined slope.

Line 4: y+1=5(x+2)y + 1 = -5(x + 2)

  • First, rewrite it in slope-intercept form: y+1=5(x+2)    y+1=5x10    y=5x11y + 1 = -5(x + 2) \implies y + 1 = -5x - 10 \implies y = -5x - 11
  • The slope of this line is 5-5.

Checking for Perpendicularity

  • Two lines are perpendicular if the product of their slopes is 1-1.
  1. Line 1 and Line 2:

    • Slope of Line 1 = 0 (horizontal line)
    • Slope of Line 2 = 15\frac{1}{5}
    • 0×15=00 \times \frac{1}{5} = 0, so they are not perpendicular.
  2. Line 1 and Line 3:

    • Line 1 has a slope of 0 (horizontal line).
    • Line 3 has an undefined slope (vertical line).
    • Horizontal and vertical lines are always perpendicular, so Line 1 and Line 3 are perpendicular.
  3. Line 1 and Line 4:

    • Slope of Line 1 = 0 (horizontal line)
    • Slope of Line 4 = 5-5
    • 0×(5)=00 \times (-5) = 0, so they are not perpendicular.
  4. Line 2 and Line 3:

    • Slope of Line 2 = 15\frac{1}{5}
    • Line 3 has an undefined slope (vertical line).
    • Horizontal lines and vertical lines are always perpendicular, so Line 2 and Line 3 are perpendicular.
  5. Line 2 and Line 4:

    • Slope of Line 2 = 15\frac{1}{5}
    • Slope of Line 4 = 5-5
    • 15×(5)=1\frac{1}{5} \times (-5) = -1, so Line 2 and Line 4 are perpendicular.
  6. Line 3 and Line 4:

    • Line 3 has an undefined slope (vertical line).
    • Slope of Line 4 = 5-5.
    • Vertical and non-vertical lines are not perpendicular.

Conclusion

  • Line 1 and Line 3 are perpendicular.
  • Line 2 and Line 4 are perpendicular.

Thus, the correct answer is "Lines 1 and 3 are perpendicular, and Lines 2 and 4 are perpendicular."

Would you like further details or any clarification?

Here are some related questions for further study:

  1. How do you determine the slope of a line from its equation in point-slope form?
  2. What is the general condition for two lines to be parallel?
  3. How can you find the equation of a line given its slope and a point on the line?
  4. What are the differences between horizontal, vertical, and sloped lines?
  5. How do you graphically check for perpendicularity between two lines?

Tip: Always remember that the slope of a vertical line is undefined, and the slope of a horizontal line is 0.

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Math Problem Analysis

Mathematical Concepts

Geometry
Algebra
Slope of a Line
Perpendicular Lines

Formulas

Slope of a line in slope-intercept form y = mx + b
Perpendicular lines condition: m1 * m2 = -1
Horizontal lines have slope 0
Vertical lines have undefined slope

Theorems

Two lines are perpendicular if the product of their slopes is -1

Suitable Grade Level

Grades 7-10