What is the best method to solve -2+4k^2=-15

Geometry answer picture question pls . reason and statements

What is the inverse of the function f(x)=4x+8

Dylan and dusty plan to take weekly surfing lessons together. if the 2-hour lessons are $20 per person and they plan to spend $100 each on new surfboards, what is the maximum number of lessons the two can take if the total amount spent for lessons and surfboards is at most $480?