To analyze the situation properly, let's break down the information and the statements provided:
- Original cost: The original cost of the laptop model one year ago was \( x \).
- Current cost: The current cost is represented by the expression given (though the specific current expression isn't provided in the prompt). However, based on the options, we can infer some things.
- Increase or Decrease: The key percentages involve a 21% decrease or a 79% increase from the original price.
Let's explore the implications of the statements:
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The cost of the laptop model increased by 79%:
- If the cost increased by 79%, the new cost would be \( x + 0.79x = 1.79x \). This implies the cost is more than the original cost, which contradicts any mention of a decrease. This statement seems false.
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An equivalent expression that represents this situation is \( x + 0.21x \):
- The expression \( x + 0.21x = 1.21x \) implies a 21% increase. Hence it does not match the current scenario if there's said to be a decrease. So this statement is false.
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The cost of the laptop model decreased by 21%:
- A 21% decrease would mean the new cost is \( x - 0.21x = 0.79x \). This means the cost decreased, hence this statement is true.
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An equivalent expression that represents this situation is \( x + 0.79x \):
- The expression \( x + 0.79x = 1.79x \) suggests an increase, not a decrease. Thus, this statement is false.
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An equivalent expression that represents this situation is \( x - 0.21x \):
- This simplifies to \( 0.79x \), which indeed reflects a 21% decrease, so this statement is true.
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An equivalent expression that represents this situation is \( x - 0.79x \):
- This simplifies to \( 0.21x \), indicating a very low cost, which doesn't match the scenario of being a decrease from the original. Hence, this statement is false.
In conclusion, the true statements about the situation are:
- The cost of the laptop model decreased by 21%.
- An equivalent expression that represents this situation is \( x - 0.21x \).
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