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翻阅近几年全国各省市中考试卷,不难发现有关求一元二次方程中字母系数的题型,频频出现。本文归纳其常见解法,供同学们复习时参考。 1.利用一元二次方程的定义求解 例1.(m~2-n-2)x~2+mx+3=0是关于x的一元二次方程,则m的取值范围是( )。 (A)m≠1 (B)m≠2 (C)m≠-1且m≠2 (D)一切实数 (1994,贵阳市中考题) 解 由定义知m~2-m-2≠0,解得m≠-1,且m≠2,故选C。
Looking through the examination papers of various provinces and cities in recent years, it is not difficult to find the question types that are used to find the letter coefficients in the quadratic equation of one dollar, and they frequently appear. This article summarizes its common solution for reference when students review. 1. Solve using the definition of a quadratic equation. Example 1. (m~2-n-2)x~2+mx+3=0 is a quadratic equation about x, so the range of m is (). (A) m ≠ 1 (B) m ≠ 2 (C) m ≠ -1 and m ≠ 2 (D) All real numbers (1994, Guiyang examination questions) Solution definition m~2-m-2≠ 0 Solution m≠-1, and m≠2, so choose C.