Determine which relation is a function

The suare root of 9x plus 7 plus the square rot of 2x equall to 7

Use composition to determine if (x) or h(x) is the inverse of f(x) for the limited domain x2-1.

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)