Mrs.D Math · 8th Grade

FUNCTION
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Slope & Y-Intercept · Comparing Functions
📈 Functions
📑 Linear Equations
⭐ y = mx + b
💵 y = 2.50x + 2
📊 vs. the Table
🏆 Find the Best Deal!
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📚 Comparing Functions

Two Ways to Show the Same Kind of Rule

One option gives an equation (y = mx + b). The other gives a table. Both are functions — find the cost of each, then compare!

1
Equation option: plug the number of items in for x.
y = 2.50x + 2  →  y = 2.50(6) + 2 = 15 + 2 = $17
2
Table option: find the pattern (the rule), then extend it.
1→3.00, 2→6.00, 3→9.00  →  y = 3x → 3(6) = $18
3
Compare: $17 vs $18 — online is cheaper for 6 books!

Reading the Table Like a Pro

✓
If y goes up by the same amount each time x goes up by 1, that amount is the slope m.
✓
If the table skips (x = 2, 4, 6...), divide the change in y by the change in x.
✓
Work backward toward x = 0 to find the y-intercept b (the starting fee).

How to Play

💸
Cheaper — pick the option that costs LESS, with its correct total.
💰
Pricier — pick the option that costs MORE, with its correct total.
🆕
Mixed — read carefully! Cheaper and pricier questions shuffled together.
🧮
Your calculator lives in the bottom-left corner — but try it in your head first!
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