An icicle drips at a rate that can be represented by the function f(x)=-x^2+8x-7 . where 0< x< 10 and x is the number of hours after the sun has risen. when f(x) is a negative number, the icicle is not dripping. determine the values when the icicle starts and stops dripping.
x=-1 and x=7
x=1 and x=7
x=1 and x=-7
x=-1 and x=-7