Please help (algebra)

What is the vertex form of f(x) = x2 + 6x + 3

Drag each sequence of transformations to the correct location on the table. classify the sequences of transformations based on whether or not they prove the congruency of the shapes by mapping shape i onto shape ii. plz i'll rate u 5 stars need this done for a mastery test

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?