### Home > PC > Chapter 7 > Lesson 7.3.3 > Problem7-128

7-128.

Solve each inequality.

1. $\left(1 − x\right)\left(x − 3\right)\left(x − 5\right) \gt 0$

The $\gt$ sign means you need $3$ factors when multiplied are positive.
Check values in the intervals about the zeros to find these positive intervals.
Write the answer in interval notation.

$\left(−∞,1\right) ∪ \left(3,5\right)$

1. $x^{2} − 2x − 15 \lt 0$

1. Factor and find the zeros.
2. Use the line below to test your intervals.
3. How many factors do you have?
4. Should they multiply to a positive or negative number?