Writing Equations Using Two Points
Grade 7 students in Big Ideas Math Advanced 2 (Chapter 4: Graphing and Writing Linear Equations) learn to write linear equations using two given points by first calculating slope, then applying point-slope form. If slope is undefined, the line is vertical with equation x = c.
Key Concepts
When given two points, first find the slope using the formula $m = \frac{y 2 y 1}{x 2 x 1}$. Then, choose one of the points and use the point slope form, $y y 1 = m(x x 1)$, to write the equation of the line.
Common Questions
How do you write a linear equation from two points in 7th grade?
Step 1: Find slope using m = (y2 - y1) / (x2 - x1). Step 2: Choose one point and substitute into point-slope form: y - y1 = m(x - x1).
How do you write the equation through (2, 3) and (4, 7)?
Slope: m = (7-3)/(4-2) = 2. Using point (2,3): y - 3 = 2(x - 2).
What do you do when the slope is undefined?
Undefined slope means a vertical line. The equation is x = c, where c is the x-coordinate shared by both points.
What chapter in Big Ideas Math Advanced 2 covers writing equations from two points?
Chapter 4: Graphing and Writing Linear Equations in Big Ideas Math Advanced 2 (Grade 7) covers writing equations using two points.
Can you use either point when applying point-slope form?
Yes. Both points lie on the same line, so either point gives the same equation. Choose the simpler coordinates to minimize arithmetic errors.