To identify where the error using the Commutative Property of Addition occurs, let's analyze the steps in detail.
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Step 1:
- Original expression: \( 8 + x^2 + 17x - x^2 + 4 = 10 + 4x^2 + 10x - 4x^2 + 2 + 7x \)
- Simplified: \( 8 + 4 + x^2 - x^2 + 17x = 10 + 2 + 10x - 4x^2 + 7x + 4x^2 \)
- This step appears to rearrange and group correctly according to the Commutative Property.
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Step 2:
- Simplified version: \( 8 + 4 + 17x + x^2 - x^2 = 10 + 2 + 4x^2 - 4x^2 + 10x + 7x \)
- Here, the simplification seems valid, but it seems the order of terms was not fully rearranged correctly (from the left original expression to correctly match the right side).
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Step 3:
- This gives us: \( 12 + 17x + x^2 = 12 - x^2 + 17x \)
- Here, combining like terms seems to have introduced the term "\(-x^2\)" incorrectly because \(x^2 - x^2\) cancels out on the left side.
Therefore, the actual mistake occurs in Step 3, where the resulting equation incorrectly shows \(-x^2\) instead of simplifying fully.
Final answer: Step 3.