Write an Equation in Slope-Intercept Form From Two Points

🔑 Key Concepts

  • Use both ordered pairs to calculate the slope with \(\displaystyle m=\frac{y_2-y_1}{x_2-x_1}\).
  • Substitute the slope and either known point into \(y=mx+b\).
  • Solve the resulting equation to determine the y-intercept, \(b\).
  • Substitute \(m\) and \(b\) into \(y=mx+b\) to write the final equation.
  • Check that both original ordered pairs satisfy the completed equation.

💡 Main Idea

When two points are given, first use them to calculate the slope. Then substitute the slope and the \(x\)- and \(y\)-coordinates of either point into \(y=mx+b\). Solve for \(b\), and use the slope and y-intercept to write the equation in slope-intercept form.

✏️ Worked Examples — Writing \(y=mx+b\) from Two Points

🧠 Math Vocabulary

  • Slope-intercept form: The form \(y=mx+b\), where \(m\) is the slope and \(b\) is the y-intercept.
  • Slope: The rate of change between two points, calculated as change in \(y\) divided by change in \(x\).
  • Y-intercept: The value of \(y\) where a line crosses the y-axis.
  • Ordered pair: A point written as \((x,y)\).
  • Substitution: Replacing a variable with a known value.

📚 What You Should Already Know

Before this lesson, students should understand ordered pairs, integer operations, substitution, solving one-step equations, and how to calculate slope from two points.

🚀 What Comes Next

Students can use the completed equation to graph the line, compare linear relationships, write equations from tables and graphs, and model real-world situations with slope and y-intercept.

🧩 Embed This Video in Your LMS

Teachers can embed this YouTube video directly into Canvas, Google Classroom, Schoology, or another learning platform. Click below to show the embed code.