本题可先根据\(x = \frac{\sqrt{5} – 1}{2}\)推出\(2x + 1 = \sqrt{5}\),两边平方得到x的二次方程,再通过降次逐步求出\(x^6\)。
步骤一:对\(x = \frac{\sqrt{5} – 1}{2}\)进行变形
由\(x = \frac{\sqrt{5} – 1}{2}\),等式两边同时乘以2可得\(2x=\sqrt{5}-1\),移项得到\(2x + 1 = \sqrt{5}\)。
步骤二:求出x满足的二次方程
对\(2x + 1 = \sqrt{5}\)两边同时平方,根据完全平方公式\((a+b)^2=a^2 + 2ab + b^2\)可得: \((2x + 1)^2 = (\sqrt{5})^2\) \(4x^2 + 4x + 1 = 5\) 移项化简得\(x^2 + x – 1 = 0\),即\(x^2 = 1 – x\) ,这一步用于后续降次计算。
步骤三:计算\(x^3\)
根据同底数幂相乘\(a^m\times a^n=a^{m + n}\),\(x^3 = x^2 \cdot x\),把\(x^2 = 1 – x\)代入可得: \(x^3=(1 – x)\cdot x = x – x^2\) 再把\(x^2 = 1 – x\)代入上式,\(x^3 = x – (1 – x)=2x – 1\)
步骤四:计算\(x^6\)
\(x^6=(x^3)^2\),把\(x^3 = 2x – 1\)代入可得: \(x^6=(2x – 1)^2\) 根据完全平方公式\((a-b)^2=a^2 – 2ab + b^2\)展开得: \(x^6 = 4x^2 – 4x + 1\) 把\(x^2 = 1 – x\)代入上式: \(x^6 = 4(1 – x) – 4x + 1\) 去括号得\(x^6 = 4 – 4x – 4x + 1\) 合并同类项得\(x^6 = 5 – 8x\)
步骤五:代入x的值计算\(x^6\)
把\(x = \frac{\sqrt{5} – 1}{2}\)代入\(x^6 = 5 – 8x\)可得: \(x^6 = 5 – 8\times\frac{\sqrt{5} – 1}{2}\) \(= 5 – 4(\sqrt{5} – 1)\) \(= 5 – 4\sqrt{5} + 4\) \(= 9 – 4\sqrt{5}\)
综上,\(x^6\)的值为\(\boldsymbol{9 – 4\sqrt{5}}\)。