Let's analyze the statements one by one in relation to the given situation.
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An equivalent expression that represents this situation is x − 0.21x.
- This is true. The expression \( x - 0.21x \) simplifies to \( 0.79x \), meaning the cost of the laptop is now 79% of its original cost, which indicates a decrease of 21%.
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The cost of the laptop model increased by 79%.
- This is false. If the cost decreased by 21%, it means it did not increase by 79%; rather it decreased to 79% of its original cost.
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An equivalent expression that represents this situation is x − 0.79x.
- This is false. The expression \( x - 0.79x \) simplifies to \( 0.21x \), which would suggest that the remaining cost is only 21% of the original, indicating a decrease — this does not correctly represent the situation where the cost is now 79% of the original.
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The cost of the laptop model decreased by 21%.
- This is true. As established in the first statement, if the new cost corresponds to \( 0.79x \), that means it has decreased by 21%.
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An equivalent expression that represents this situation is x + 0.21x.
- This is false. The expression \( x + 0.21x \) simplifies to \( 1.21x \), which indicates an increase in cost by 21%, contradicting the fact that the cost decreased.
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An equivalent expression that represents this situation is x + 0.79x.
- This is false. The expression \( x + 0.79x \) simplifies to \( 1.79x \), suggesting a significant increase in cost rather than a decrease.
Summary of True Statements:
- An equivalent expression that represents this situation is \( x - 0.21x \).
- The cost of the laptop model decreased by 21%.
The rest of the statements are false given the context.