add 5y-4 and 2y^2-8y

Question

my answer is: 2y^2-3y-4

classify the following, if possible
7x^2+10xy+y^2

a)not classified
b)trinomial
c)monomial
d)binomial
My answer: trinomial

Write using positive exponents, and simplify if possible

(-3x)^-2

a)(1)/(6x^2)
b)(9)/(x^2)
c)(1)/(9x^2)
d) - (9)/(x^2)

My answer: d

all correct, except the last. The 3 is in the () that has an exponent.