Answer
$7t^4-5t$
Work Step by Step
First, look at each term separately using sum/difference rule.
$\frac{d}{dt}(1.4t^5)-\frac{d}{dt}(2.5t^2)+\frac{d}{dt}(6.7)$
Then take the derivative using the general power and constant multiple rules.
$1.4*5t^4-2.5*2t+0$
