解联立方程

Answer all questions. You should use a calculator where appropriate.

You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.

Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.

请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程；仅给出计算器答案而没有过程，不予评分。除非题目另有精度要求，非精确数值答案保留 3 位有效数字，以度为单位的角度保留 1 位小数。

用直线方程消去 $x$，把联立方程化成关于 $y$ 的二次方程。求根后回代求 $x$。

Since $2x=y+5$, substitution gives

For $y=-4/3$, we have $x=(5-4/3)/2=11/6$. For $y=-1$, we have $x=2$. The solutions are $(11/6,-4/3)$ and $(2,-1)$.