Problem 28 of 34fun-028
The balance on a coffee gift card, in dollars, after coffees are bought is . The graph of crosses the -axis at . What is ?
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Solution walkthrough1:36
- A graph crosses the -axis where its height is . So is the value of that makes .
- In , the card starts at $84 (the -intercept), and each coffee takes away $6.
- Set . Add to both sides: . Divide by : , so .
- Check: . Fourteen coffees at $6 each use up all $84.
- Traps: is where the graph crosses the -axis, is the slope, and multiplies instead of divides.