Question 122503
In gral abs(f(x)) < k with k > 0 if only if  -k < f(x) < k so

abs((x-1)/9) < 2 if only if  -2<(x-1)/9<2 if only if  -18 < x-1 < 18
if only if  -17 < x < 19 so the solution is the interval (-17,19)