Math Problem Statement

Write a slope-intercept equation for a line that passes through the points (-4, 3) and (2, -9).

Solution

The problem asks for the slope-intercept form of the equation of a line that passes through the points (4,3)(-4, 3) and (2,9)(2, -9).

To find the equation, we first need to calculate the slope (mm) using the slope formula:

m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1}

Given the points (4,3)(-4, 3) and (2,9)(2, -9), we can plug in the values:

m=932(4)=932+4=126=2m = \frac{-9 - 3}{2 - (-4)} = \frac{-9 - 3}{2 + 4} = \frac{-12}{6} = -2

So the slope (mm) is 2-2.

Now, we'll use the slope-intercept form of the line equation:

y=mx+by = mx + b

We can plug in one of the points (I'll use (2,9)(2, -9)) and the slope m=2m = -2 to solve for bb (the y-intercept):

9=2(2)+b-9 = -2(2) + b 9=4+b-9 = -4 + b b=9+4=5b = -9 + 4 = -5

Now that we have the slope m=2m = -2 and the y-intercept b=5b = -5, the equation of the line is:

y=2x5y = -2x - 5

Would you like more details on any of the steps? Here are 5 questions to extend your understanding:

  1. How do you find the equation of a line given two points?
  2. Why do we need to calculate the slope first?
  3. What does the slope-intercept form represent geometrically?
  4. How can you use another point to check the equation of the line?
  5. What happens if two points have the same x-coordinate or y-coordinate?

Tip: Always double-check the sign when subtracting coordinates, as small mistakes can affect the slope calculation.

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Math Problem Analysis

Mathematical Concepts

Algebra
Slope-Intercept Form
Linear Equations

Formulas

Slope formula: m = (y2 - y1) / (x2 - x1)
Slope-intercept form: y = mx + b

Theorems

Slope formula for linear equations

Suitable Grade Level

Grades 7-9