Chapter 6 - Section 6.8 - Exponential Growth and Decay Models; Newton's Law: Logistic Growth and Decay Models - 6.8 Assess Your Understanding - Page 488: 31

See below.

We know that two non-vertical lines are perpendicular if the product of their slopes is $-1$. We know that two non-vertical lines are parallel if their slopes are equal. Hence here $5\cdot \frac{1}{5}=1\ne-1.$ Thus they are not perpendicular. Their slopes are not equal, thus they are not perpendicular.