Given the equation 21x^2 + 10 root3xy + 31y^2 = 144

a. determine the type of conic using the discriminant

b.find the angle of rotation

c.use rotation formulas to eliminate the xy-term and sketch

I was assigned a bunch of problems just like this for homework. The only problem is that my book doesn't really give an example of this type of problem, nor did my teacher in class. If anyone could help my figure this out I would be sooo grateful. Thanks so much!