What shape is this help help help help help​

Write the point-slope form of the line passing through (2, -12) and parallel to y=3x.

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?

How do u write a function for the reflection across the y axis