18x^3+51x^2+26x+15

Decartes' Rule of signs says there are no positive roots.

The Rational Roots Theorem says that the rational roots must be of the form
±(1,3,5)/(1,2,3,6)
You can quickly see that there are no rational roots, so a numeric method is your only choice left.

What was your question, anyway?

The expression you provided is a polynomial of degree 3. It can be written in expanded form as:

18x^3 + 51x^2 + 26x + 15

To evaluate this polynomial, you need to substitute a value for x and simplify the expression.

For example, if you want to evaluate the polynomial for x = 2, you substitute x = 2 into the expression:

18(2)^3 + 51(2)^2 + 26(2) + 15

Simplifying each term, you get:

18(8) + 51(4) + 26(2) + 15

144 + 204 + 52 + 15

Combine the like terms:

= 415

Therefore, when x = 2, the polynomial expression evaluates to 415.

You can evaluate the polynomial for different values of x by substituting the desired value into the expression and following the same steps.