📚 Quadratic Simultaneous Equations: Substitution and Elimination | 二次联立方程组：代入与消元
At A-Level, simultaneous equations are no longer always two straight lines. Edexcel regularly pairs a linear equation with a quadratic, or two quadratics with each other, so the number of solutions can be 0, 1, 2 or even 4. Getting the algebra right, and knowing which method to reach for, is worth solid marks in both Pure papers.
到了 A-Level 阶段，联立方程组不再总是两条直线。Edexcel 经常把一个一次方程和一个二次方程配对，或者把两个二次方程放在一起，因此解的个数可能是 0 个、1 个、2 个甚至 4 个。把代数运算做对、并知道该用哪种方法，能在两套 Pure 试卷中稳稳拿到分数。
1. Straight Lines and Curves in One System | 同一方程组中的直线与曲线
In Edexcel A-Level Mathematics, a 'quadratic simultaneous equations' question normally means one equation of degree 1 and one of degree 2 - for example a straight line meeting a parabola, or a straight line meeting a circle. Each solution is an ordered pair (x, y) and corresponds to a point where the two graphs intersect.
在 Edexcel A-Level 数学中，所谓"二次联立方程组"题目通常是指一个一次方程配一个二次方程，例如直线与抛物线相交、或直线与圆相交。每个解都是一对有序数对 (x, y)，对应两个图像的交点。
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