Please help, choose the correct equation

Which best explains why this triangle is or is not a right triangle?

If f(x)=2x-6 and g(x)=3x+9, find (f-g)(x)

Solve the problem. a student earned grades of c, a, b, and a in four different courses. those courses had these corresponding numbers of credit hours: 4, 5, 1, and 5. the grading system assigns quality points to letter grades as follows: a = 4, b = 3, c = 2, d = 1, and f = 0. compute the grade point average (gpa) and round the result to two decimal places. 3.40 3.50 8.75 2.18