Please help :[ i don't understand

What is f(3) for the quadratic function f(x)= 2x^2+ + x - 12

Find all the angles that satisfy the equation cos(θ)=32

Aresearch study is done to find the average age of all u.s. factory workers. the researchers asked every factory worker in ohio what their birth year is. this research is an example of a census survey convenience sample simple random sample