For zeros of the function (y is the function, a function of x) we need y = 0 so that in turn means we need - 9x - 1 = 0 or - 9x = 1 (i.e. add 1 to both sides); now divide by - 9, and x = 1/-9 which is exactly the same as - 1/9 or - (1/9) and this is the only zero of the function.
or
If y = -9x - 1,
When y = 0
0 = -9x - 1
0 + 1 = -9x - 1 + 1
1 = -9x
1/9 = -9x/9
1/9 = -x
1/[9 X (-1)] = -x/-1
- (1/9) = x
When x = 0
y = (-9 X 0) - 1
y = 0 - 1
y = - 1