Math 1 · Unit 7 · Lesson 6 · part 4 of 5
What would change?
The last habit: ask what a change to a or b would do, and check it against the picture.
What would change?
The last habit: ask what a change to a or b would do, and check it against the picture. It is the family-of-graphs question, what does each number do, asked about a real model.
What if it lost 15% instead of 20%?
Then b would be 0.85 instead of 0.80. Each year the phone keeps more, so the curve falls more slowly and stays above the old one. After 3 years: 800 · 0.614 = $491 instead of $410. It would cross $200 later, in year 9 instead of year 7.
What if it cost $1,000 new?
Then a would be 1000 instead of 800. Same b, so the same shape and the same 20% loss each year, but every value is a quarter bigger. The curve starts higher and crosses $200 later, in year 8.