解方程

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。

原方程要求 $x\ne0$。乘以 $x^2$ 后，将 $x^2$ 当作一个未知数来解。

For $x\ne0$, the equation becomes $3x^4-8x^2-16=0$. Putting $u=x^2$ gives

The negative value $u=-4/3$ is impossible. Thus $x^2=4$, and the solutions are $x=\pm2$.