Grade 8 Math Test Answers | 八年级数学测试答案解析

📚 Grade 8 Math Test Answers | 八年级数学测试答案解析

This article provides a full answer key and step-by-step explanations for a Grade 8 mathematics practice test. The questions cover core topics such as algebraic expressions, linear equations, slope, the Pythagorean theorem, scientific notation, ratios, inequalities, volume, statistics, and probability. Use the explanations to identify where marks are earned and where common errors occur.

本文提供一套八年级数学模拟测试的完整答案与逐步解析。题目涵盖代数式、一次方程、斜率、勾股定理、科学计数法、比例、不等式、体积、统计和概率等核心考点。通过解析可以明确得分点，并发现常见错误。

1. Question 1 – Simplifying Algebraic Expressions | 第1题 – 化简代数式

Question: Simplify 3x + 5x − 2x + 7.

题目：化简 3x + 5x − 2x + 7。

Answer: 6x + 7

答案：6x + 7

Explanation: Combine like terms 3x + 5x − 2x. Add the coefficients: 3 + 5 − 2 = 6, so the x-term becomes 6x. The constant 7 does not have a like term, so it stays as +7. Therefore, the simplified expression is 6x + 7.

解析：合并同类项 3x + 5x − 2x。将系数相加：3 + 5 − 2 = 6，所以含 x 的项变为 6x。常数 7 没有同类项，因此保持不变。化简结果为 6x + 7。

Exam tip: Only terms with exactly the same variable part can be combined. Do not add x-terms to constant terms.

考试提示：只有变量部分完全相同的项才能合并。不要把含 x 的项与常数项相加。

2. Question 2 – Solving a Linear Equation | 第2题 – 解一元一次方程

Question: Solve 4x − 7 = 13.

题目：解方程 4x − 7 = 13。

Answer: x = 5

答案：

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