Math Problem Statement

Consider the line y = 7/9x + 1. Find the equation of the line that is parallel to this line and passes through the point (-7, 4). Find the equation of the line that is perpendicular to this line and passes through the point (-7, 4).

Solution

In this problem, we are given the line equation:

y=79x+1y = \frac{7}{9}x + 1

We are tasked with finding two lines:

  1. The equation of a line parallel to the given line and passing through the point (7,4)(-7, 4).
  2. The equation of a line perpendicular to the given line and passing through the point (7,4)(-7, 4).

Step 1: Line parallel to the given line

Parallel lines have the same slope. The slope of the given line is 79\frac{7}{9}. So, the slope of the parallel line will also be 79\frac{7}{9}.

To find the equation of the parallel line that passes through (7,4)(-7, 4), we use the point-slope form of the line equation:

yy1=m(xx1)y - y_1 = m(x - x_1)

where mm is the slope and (x1,y1)(x_1, y_1) is the point through which the line passes. Plugging in the values:

m=79,(x1,y1)=(7,4)m = \frac{7}{9}, \quad (x_1, y_1) = (-7, 4)

y4=79(x+7)y - 4 = \frac{7}{9}(x + 7)

Now simplify this equation:

y4=79x+79×7y - 4 = \frac{7}{9}x + \frac{7}{9} \times 7 y4=79x+499y - 4 = \frac{7}{9}x + \frac{49}{9}

Adding 4 to both sides:

y=79x+499+4y = \frac{7}{9}x + \frac{49}{9} + 4

Convert 4 to a fraction with a denominator of 9:

y=79x+499+369y = \frac{7}{9}x + \frac{49}{9} + \frac{36}{9}

y=79x+859y = \frac{7}{9}x + \frac{85}{9}

So the equation of the parallel line is:

y=79x+859y = \frac{7}{9}x + \frac{85}{9}

Step 2: Line perpendicular to the given line

The slope of a line perpendicular to another is the negative reciprocal of the original line's slope. Since the slope of the given line is 79\frac{7}{9}, the slope of the perpendicular line will be 97-\frac{9}{7}.

To find the equation of the perpendicular line passing through (7,4)(-7, 4), again using the point-slope form:

y4=97(x+7)y - 4 = -\frac{9}{7}(x + 7)

Now simplify this equation:

y4=97x97×7y - 4 = -\frac{9}{7}x - \frac{9}{7} \times 7 y4=97x9y - 4 = -\frac{9}{7}x - 9

Add 4 to both sides:

y=97x9+4y = -\frac{9}{7}x - 9 + 4

y=97x5y = -\frac{9}{7}x - 5

Thus, the equation of the perpendicular line is:

y=97x5y = -\frac{9}{7}x - 5

Summary:

  • The equation of the parallel line is: y=79x+859y = \frac{7}{9}x + \frac{85}{9}
  • The equation of the perpendicular line is: y=97x5y = -\frac{9}{7}x - 5

Do you need any further clarification or details on these steps? Here are some related questions for you to explore:

  1. How can you convert the point-slope form of a line into the slope-intercept form?
  2. What happens if the two lines are parallel but have different y-intercepts?
  3. How do you find the intersection of two perpendicular lines?
  4. How does the slope of a line affect its steepness?
  5. How can you apply the concept of parallel and perpendicular lines in geometry?

Tip: Always remember that parallel lines have equal slopes, and perpendicular lines have slopes that are negative reciprocals of each other!

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Slope
Parallel Lines
Perpendicular Lines
Point-Slope Form

Formulas

Point-Slope Formula: y - y_1 = m(x - x_1)
Slope of perpendicular lines: m_1 * m_2 = -1

Theorems

Slope of parallel lines is equal
Slope of perpendicular lines is the negative reciprocal

Suitable Grade Level

Grades 8-10