·
·
¡Hola Oscar!
El triangulito ese significa incremento.
$$\begin{align}&\Delta x = 0.85-0.7=0.15\\&\\&\frac{\Delta y}{\Delta x}=\frac{0.85^2+4·0.85-(0.7^2+4·0.7)}{0.15}=\\&\\&\frac{0.7225+3.4-0.49-2.8}{0.15}=\frac{0.8325}{0.15}=5.55\end{align}$$:
:
