Math Problem Statement

Write the equation of the line that passes through the points (7, –4) and (–1, 3), first in point-slope form, and then in slope-intercept form.

Solution

To find the equation of the line passing through the points (7,4)(7, -4) and (1,3)(-1, 3), we’ll first calculate the slope and then use point-slope form.

Step 1: Calculate the Slope

The formula for the slope mm between two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is: m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1} Substituting (x1,y1)=(7,4)(x_1, y_1) = (7, -4) and (x2,y2)=(1,3)(x_2, y_2) = (-1, 3): m=3(4)17=3+48=78=78m = \frac{3 - (-4)}{-1 - 7} = \frac{3 + 4}{-8} = \frac{7}{-8} = -\frac{7}{8}

Step 2: Write in Point-Slope Form

The point-slope form of a line with slope mm passing through a point (x1,y1)(x_1, y_1) is: yy1=m(xx1)y - y_1 = m(x - x_1) Using the point (7,4)(7, -4) and the slope 78-\frac{7}{8}: y+4=78(x7)y + 4 = -\frac{7}{8}(x - 7) This is the point-slope form of the line.

Step 3: Convert to Slope-Intercept Form

Now, let’s simplify this equation to the slope-intercept form, y=mx+by = mx + b: y+4=78x+498y + 4 = -\frac{7}{8}x + \frac{49}{8} Subtract 4 from both sides to isolate yy: y=78x+4984y = -\frac{7}{8}x + \frac{49}{8} - 4 To combine terms, convert 4 to a fraction with a denominator of 8: y=78x+498328y = -\frac{7}{8}x + \frac{49}{8} - \frac{32}{8} y=78x+178y = -\frac{7}{8}x + \frac{17}{8}

Final Answer

  • Point-Slope Form: y+4=78(x7)y + 4 = -\frac{7}{8}(x - 7)
  • Slope-Intercept Form: y=78x+178y = -\frac{7}{8}x + \frac{17}{8}

Would you like further details or have any questions?


Here are five related questions for practice:

  1. What is the equation of a line passing through points (3,2)(3, 2) and (6,1)(6, -1)?
  2. How do you find the y-intercept of a line given two points?
  3. How can you convert a point-slope form equation to standard form?
  4. What does the slope of a line tell you about the line's direction?
  5. How would you find the x-intercept of the line we just found?

Tip: When finding the slope, always subtract consistently in the same order to avoid sign errors.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Equations
Slope
Point-Slope Form
Slope-Intercept Form

Formulas

Slope formula: m = (y2 - y1) / (x2 - x1)
Point-Slope Form: y - y1 = m(x - x1)
Slope-Intercept Form: y = mx + b

Theorems

Slope formula
Point-Slope form
Slope-Intercept form

Suitable Grade Level

Grades 7-9