Math Problem Statement

A line passes through the points ( – 8,9) and ( – 2, – 9). Write its equation in slope-intercept form.

Solution

To find the equation of the line passing through the points (8,9)(-8, 9) and (2,9)(-2, -9), we need to follow these steps:

Step 1: Calculate the slope (m)

The slope of a line passing through two points (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is given by the formula:

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

Substitute the given points (8,9)(-8, 9) and (2,9)(-2, -9):

m=992(8)=182+8=186=3m = \frac{-9 - 9}{-2 - (-8)} = \frac{-18}{-2 + 8} = \frac{-18}{6} = -3

So, the slope m=3m = -3.

Step 2: Use the point-slope form

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

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

We can use one of the given points, say (8,9)(-8, 9), and substitute the slope m=3m = -3 into the equation:

y9=3(x+8)y - 9 = -3(x + 8)

Step 3: Simplify to slope-intercept form

Now, let's simplify this equation into the slope-intercept form y=mx+by = mx + b.

y9=3(x+8)y - 9 = -3(x + 8) y9=3x24y - 9 = -3x - 24 y=3x24+9y = -3x - 24 + 9 y=3x15y = -3x - 15

Final equation

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

y=3x15y = -3x - 15

Would you like any further explanation on this?

Here are 5 related questions for further practice:

  1. How do you find the equation of a line when given the slope and a point?
  2. What is the meaning of the slope in the context of a line?
  3. How can you convert a line from standard form to slope-intercept form?
  4. How do you determine if two lines are parallel or perpendicular using their slopes?
  5. How do you find the x-intercept and y-intercept of a line?

Tip: Always double-check the slope calculation before proceeding with the equation to avoid mistakes.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Equations
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-Intercept Theorem

Suitable Grade Level

Grades 8-10