To simplify the polynomial expression \((r - 1)(r^2 - 2r + 3)\), we will distribute \(r - 1\) to each term in \(r^2 - 2r + 3\).
Let's start with the distribution:
\[ (r - 1)(r^2 - 2r + 3) = r(r^2 - 2r + 3) - 1(r^2 - 2r + 3) \]
Now, distribute \(r\):
\[ r(r^2) + r(-2r) + r(3) = r^3 - 2r^2 + 3r \]
Next, distribute \(-1\):
\[ -1(r^2) + (-1)(-2r) + (-1)(3) = -r^2 + 2r - 3 \]
Now, combine both results:
\[ r^3 - 2r^2 + 3r - r^2 + 2r - 3 \]
Combine like terms:
- The \(r^2\) terms: \(-2r^2 - r^2 = -3r^2\)
- The \(r\) terms: \(3r + 2r = 5r\)
- The constant term is \(-3\).
Putting it all together, we get:
\[ r^3 - 3r^2 + 5r - 3 \]
So, the simplified form of the polynomial expression \((r - 1)(r^2 - 2r + 3)\) is:
\[ \boxed{r^3 - 3r^2 + 5r - 3} \]