Three roots of a fourth-degree polynomial equation with rational coefficients are 5 + , −17, and 2 – . Which number is also a root of the equation?

It seems like there's a mistake in your question as the roots "5 + " and "2 - " are incomplete. However, if you're referring to complex roots, it's important to note that complex roots always come in conjugate pairs if the coefficients are rational numbers.

This means that if (5 + i) is a root, then (5 - i) is also a root. Similarly, if (2 - i) is a root, then (2 + i) is also a root.

So, if the roots you intended to write were (5 + i), -17, and (2 - i), then the fourth root would be (2 + i). If the roots were (5 - i), -17, and (2 + i), then the fourth root would be (5 + i).

Please provide the complete roots for a more accurate answer.