Review question

# If we increase $x$ by a small amount, what happens to $y$? Add to your resource collection Remove from your resource collection Add notes to this resource View your notes for this resource

Ref: R9942

## Suggestion

Hence find the approximate increase in $x$ which will cause $y$ to increase from $4$ to $4.05$.

Suppose $y = f(x)$, and that $(x,y)$ is on this curve. We now increase $x$ by a small amount $\delta x$, which increases $y$ by a small amount $\delta y$ ($y$ could decrease, in which case $\delta y$ would be negative).

Can you see why $y'$ evaluated at $x$ is roughly $\dfrac{\delta y}{\delta x}$? A diagram might help…