(x - 15)*(x + 2) < (x + 1)*(x - 9)
(x - 15)*(x + 2) < (x - 9)*(x + 1)
And(-21/5 < x, x < oo)
(-21/5 < x)∧(x < oo)
(-21/5, oo)
x in Interval.open(-21/5, oo)