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Two charges have exactly the same rate of change, but one adds an extra £15 to every total. How do their two lines compare on the same axes?
AOne sits 15 above the other, equally steep
BOne is 15 times steeper than the other one
COne crosses the other after 15 units used
DOne slopes up while the other slopes down
Answer & Solution
Correct answer: A. One sits 15 above the other, equally steep
1. The number added on its own shifts the whole line up or down the page.
2. It has no effect at all on the steepness, which is set by the rate of change.
3. Both rules share the same rate here, so both lines are equally steep.
4. Adding £15 lifts one line 15 units above the other at every input value.
5. Option B confuses adding 15 with multiplying by 15, which would change the steepness instead.
_Source: OpenStax College Algebra (CC BY 4.0), Ch 4 "Linear Functions", section 4.1 Linear Functions_
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