The expression you've provided is \( 9x^2 - 6x - 15 \).

To simplify or factor this expression, you can follow these steps:

1. **Factor out the greatest common factor (GCF)**:
The GCF of the coefficients (9, -6, -15) is 3. So we can factor out 3:

\[
3(3x^2 - 2x - 5)
\]

2. **Factor the quadratic**:
We need to factor the quadratic \( 3x^2 - 2x - 5 \). We'll look for two numbers that multiply to \( 3 \times -5 = -15 \) and add to -2.

The numbers -5 and 3 fit this requirement. This gives:

\[
3x^2 - 5x + 3x - 5
\]

Grouping the terms, we have:

\[
(3x^2 - 5x) + (3x - 5) = x(3x - 5) + 1(3x - 5) = (3x - 5)(x + 1)
\]

Thus, the factored form of the original expression is:

\[
3(3x - 5)(x + 1)
\]

If you want to find the roots, you can set \( 3(3x - 5)(x + 1) = 0 \) and solve for \( x \).