Explain in complete sentences and using an example when an equation has "infinite solutions" also known as "all real numbers"

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?

If f(x)= sqrt4x+9+2, which inequality can be used to find the domain of f(x)?

The focus of parabola is (-4, -5), and its directrix is y= -1. fill in the missing terms and signs in parabolas equation in standard form