Find the constant of variation k for the direct variation. 3x+5y=0

Astuntman jumping off a 20-m-high building is modeled by the equation h=20-5t^2, where t is the same in seconds. a high-speed camera is ready to film him between 15m and 10m above the ground. for which interval of time should the camera film him?

What are the solutions of the equation x4 + 6x2 + 5 = 0? use u substitution to solve.

Marking brainliest for original answer.. are these two triangles similar? how can you tell?