Math Problem Statement

Write the equation of the line that passes through the points left parenthesis, 9, comma, minus, 4, right parenthesis(9,−4) and left parenthesis, 2, comma, minus, 2, right parenthesis(2,−2). Put your answer in fully simplified point-slope form, unless it is a vertical or horizontal line.

Solution

To determine the equation of the line that passes through the points (9,4)(9, -4) and (2,2)(2, -2), follow these steps:


1. Find the slope (mm) of the line.

The formula for the slope between two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is:
m=y2y1x2x1.m = \frac{y_2 - y_1}{x_2 - x_1}.
Substitute (x1,y1)=(9,4)(x_1, y_1) = (9, -4) and (x2,y2)=(2,2)(x_2, y_2) = (2, -2):

m=2(4)29.m = \frac{-2 - (-4)}{2 - 9}.

Simplify the numerator and denominator:

m=2+429=27.m = \frac{-2 + 4}{2 - 9} = \frac{2}{-7}.

Thus, the slope is:

m=27.m = -\frac{2}{7}.


2. Use the point-slope form of a line.

The point-slope form of a line is:
yy1=m(xx1),y - y_1 = m(x - x_1), where mm is the slope, and (x1,y1)(x_1, y_1) is any point on the line.
We can use one of the given points, say (9,4)(9, -4), and m=27m = -\frac{2}{7}.

Substitute these values into the formula:

y(4)=27(x9).y - (-4) = -\frac{2}{7}(x - 9).

Simplify the equation:

y+4=27(x9).y + 4 = -\frac{2}{7}(x - 9).


3. Fully simplified point-slope form.

The equation of the line in point-slope form is:

y+4=27(x9).y + 4 = -\frac{2}{7}(x - 9).

This is the required equation of the line.


Let me know if you'd like the equation in slope-intercept form or if you have any questions! Here are 5 related problems:

  1. Find the equation of the line that passes through (3,5)(3, 5) and (7,1)(7, 1).
  2. Write the equation of a vertical line passing through (4,2)(4, -2).
  3. Determine the slope of the line passing through (1,6)(1, -6) and (4,3)(4, 3).
  4. Convert y+4=27(x9)y + 4 = -\frac{2}{7}(x - 9) to slope-intercept form.
  5. Write the equation of a horizontal line passing through (3,5)(-3, 5).

Tip: Always calculate the slope carefully, as sign errors are common!

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Point-Slope Form
Slope

Formulas

Slope formula: m = (y2 - y1) / (x2 - x1)
Point-Slope form: y - y1 = m(x - x1)

Theorems

Slope of a line
Point-Slope form of a line

Suitable Grade Level

Grades 8-10