To simplify the expression \((r-1)(r^2-2r+3)\), we can use the distributive property (also known as the FOIL method for binomials).
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Distribute \(r\) across the terms in the second parenthesis: \[ r \cdot (r^2) + r \cdot (-2r) + r \cdot 3 = r^3 - 2r^2 + 3r \]
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Distribute \(-1\) across the terms in the second parenthesis: \[ -1 \cdot (r^2) - 1 \cdot (-2r) - 1 \cdot 3 = -r^2 + 2r - 3 \]
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Now combine the results from steps 1 and 2: \[ r^3 - 2r^2 + 3r - r^2 + 2r - 3 \]
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Combine like terms:
- The \(r^2\) terms: \(-2r^2 - r^2 = -3r^2\)
- The \(r\) terms: \(3r + 2r = 5r\)
Putting it all together, we have: \[ r^3 - 3r^2 + 5r - 3 \]
Thus, the simplified form of the expression \((r-1)(r^2-2r+3)\) is: \[ \boxed{r^3 - 3r^2 + 5r - 3} \]