Answer:
(-8.89, -26.69)
Explanation:
To find the point with coordinates of the form (a, 3a) that is in the third quadrant and is a distance 5 from P(2,1), we can use the following steps:
- Since the point is in the third quadrant, both the x-coordinate and the y-coordinate must be negative. Therefore, we can write (a, 3a) as (-|a|, -3|a|).
- We know that the distance between P(2,1) and (-|a|, -3|a|) is 5. We can use the distance formula to set up an equation and solve for |a|:

- Squaring both sides of the equation and simplifying, we get:

- Solving for a using the quadratic formula, we get:

- Since the point is in the third quadrant, we want the negative root, so:

- Substituting this value of a into (-|a|, -3|a|), we get:
(x, y) =

(x, y) ≈ (-8.89, -26.69)
Therefore, the point with coordinates of the form (a, 3a) that is in the third quadrant and is a distance 5 from P(2,1) is approximately (-8.89, -26.69).