Math Problem Statement

Write the equation of the line that passes through the points (−3,−7) and(9,1). Put your answer in fully simplified point-slope form, unless it is a vertical or horizontal line.

Solution

To find the equation of the line passing through the points (3,7)(-3, -7) and (9,1)(9, 1), we first need to calculate the slope of the line using the slope formula:

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

Substitute the given points (3,7)(-3, -7) and (9,1)(9, 1) into the formula:

m=1(7)9(3)=1+79+3=812=23m = \frac{1 - (-7)}{9 - (-3)} = \frac{1 + 7}{9 + 3} = \frac{8}{12} = \frac{2}{3}

Now that we have the slope m=23m = \frac{2}{3}, we use the point-slope form of the equation of a line:

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

We can use either point. Let's use (3,7)(-3, -7):

y(7)=23(x(3))y - (-7) = \frac{2}{3}(x - (-3))

Simplifying:

y+7=23(x+3)y + 7 = \frac{2}{3}(x + 3)

Thus, the equation of the line in point-slope form is:

y+7=23(x+3)y + 7 = \frac{2}{3}(x + 3)

Let me know if you'd like further details or explanations!

Here are 5 related questions to explore:

  1. How can you convert this equation to slope-intercept form?
  2. What is the equation if we use the point (9,1)(9, 1) instead?
  3. How do we find the x-intercept of this line?
  4. Can this equation be expressed in standard form?
  5. What happens if the slope between two points is zero?

Tip: The point-slope form is very useful when you know one point and the slope of a line—it allows you to write the equation quickly without needing the y-intercept!

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Equations
Slope of a Line

Formulas

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

Theorems

Slope formula
Point-slope form theorem

Suitable Grade Level

Grades 8-10