Worked Examples · Example 9
Q.Find the derivative of .
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Start your 14-day free trial to unlock the full solution →The derivative measures the rate of change of a function; for , the output changes by units for every unit change in , so .
Understanding the derivative at a point
The derivative of a function at any point tells us how fast the function is changing there. For a linear function like , the graph is a straight line through the origin with slope . This slope is constant everywhere—the function climbs by units vertically for every unit we move horizontally. That constant rate of change is the derivative.
We can verify this using the limit definition of the derivative:
This formula captures the idea of "rise over run" as the run shrinks to zero.
Step-by-step calculation
- Substitute into the definition. We have , so . The difference quotient becomes:
- Simplify before taking the limit. As long as (which is fine, since we're taking a limit as approaches zero, not equals it), we can cancel:
- Evaluate the limit. …
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