math class 678 4-in-1 skill sheets
Slope from Two Points, Algebra 1 4-in-1 Skill Sheet (HSF.IF.B.6)
HSF.IF.B.6 Algebra 1 Unit 5: Linear Functions and Graphing

Slope from Two Points

I can find the slope through two points by subtracting y over x in the same order.

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The problem this sheet solves

This is an ORDER error, not an inversion error. Students subtract y in one direction and x in the other, which flips the sign while leaving the magnitude right, so a student who checks the size of their answer sees nothing wrong. It is a different mistake from reading slope off a graph, and it needs its own attention. This sheet fixes a starting point and requires the same point first on top and bottom, which removes the error at its source rather than correcting it afterwards. Subscripts are explained as labels rather than operations, and the sheet covers the zero and undefined cases so a zero in the denominator is recognised instead of divided through.

The key rule

slope = y2 − y1/x2 − x1. Start from the SAME point on top and bottom. Swapping the order on only one of them flips the sign.

Same point first, top and bottom.

Watch out

The mistake: A student finds the slope through (3, 9) and (7, 1) by working out 1 − 9 on top but 3 − 7 underneath, and answers 2.

The fix: The top started at the second point and the bottom started at the first. Pick one point to start from and use it both times: the slope is -2, not 2.

What is included

  • Reference page — student-friendly definitions, a worked example, a Watch Out error pair, and the key rule
  • Practice page — six problems, building from foundational to multi-step
  • Apply page — a word problem, a reasoning prompt, and an error-analysis task
  • Assess — a half-page exit ticket, two to a sheet, with a score box
  • Full answer key — every item worked, plus a grading guide that says what each wrong answer tells you
  • Ink-saver edition of all 7 pages
  • 14-slide teacher deck (PowerPoint) with presenter notes on every slide

Standard codes refer to the Common Core State Standards for Mathematics. Math Class 678 is an independent publisher, not affiliated with, sponsored by, or endorsed by NGA Center or CCSSO. Every product is sold on Teachers Pay Teachers.