Solve the inequality and select the solution set in interval notation: (x + 3)(x - 5) < 0?

Question

A. (-∞, -3) U (5, ∞)
B. (-∞, -5) U (3, ∞)
C. (-3, 5)
D. No solutions

Answer 1

The parabola y = (x+3)(x-5) crosses the x axis at -3 and 5. It opens upward, so its vertex must be below the x axis. So y < 0 for x in (-3, 5).

Answer 2

x+3<0
x<-3
s.s=]-infinity,-3[
or
x-5<0
x<5
s.s=]-infinity,5[

answer ]-infinity,-3[