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数学分步求解
一元二次方程、三次方程和反函数求解，展示每一步过程。多数试卷的分数给在方法上，答案对但没有过程拿不到几分。
b² − 4ac 在你动手之前就告诉你答案的性质：正数两个实根，零一个重根，负数没有实根。判别式是完全平方数时才能在整数范围内因式分解。
先用有理根定理找到一个根——测试常数项的因数除以首项系数的因数。找到根 r 后用综合除法除以 (x − r)，剩下的就是你已经会解的二次式。
只有学会方法才有用，所以每个求解器都打印完整过程。考场上要的是你能自己走一遍。
代回去检验 f(f⁻¹(x)) = x，成立才对。
