Hill Long
05/27/2024 · Primary School
If \( x^{2}-7 x+1=0 \), what is \( x+\frac{1}{x}-7 ? \)
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Step-by-step Solution
Given the equation \( x^{2}-7x+1=0 \), we need to find the value of \( x+\frac{1}{x}-7 \).
To find the value of \( x+\frac{1}{x}-7 \), we first need to solve the equation \( x^{2}-7x+1=0 \) to find the values of \( x \).
Let's solve the equation \( x^{2}-7x+1=0 \) using the quadratic formula.
Solve the quadratic equation by following steps:
- step0: Solve using the quadratic formula:
\(x^{2}-7x+1=0\)
- step1: Solve using the quadratic formula:
\(x=\frac{7\pm \sqrt{\left(-7\right)^{2}-4}}{2}\)
- step2: Simplify the expression:
\(x=\frac{7\pm \sqrt{45}}{2}\)
- step3: Simplify the expression:
\(x=\frac{7\pm 3\sqrt{5}}{2}\)
- step4: Separate into possible cases:
\(\begin{align}&x=\frac{7+3\sqrt{5}}{2}\\&x=\frac{7-3\sqrt{5}}{2}\end{align}\)
- step5: Rewrite:
\(x_{1}=\frac{7-3\sqrt{5}}{2},x_{2}=\frac{7+3\sqrt{5}}{2}\)
The solutions to the equation \( x^{2}-7x+1=0 \) are \( x_{1}=\frac{7-3\sqrt{5}}{2} \) and \( x_{2}=\frac{7+3\sqrt{5}}{2} \).
Now, we can substitute these values of \( x \) into the expression \( x+\frac{1}{x}-7 \) to find the value. Let's calculate it.
Calculate the value by following steps:
- step0: Calculate:
\(\frac{7-3\sqrt{5}}{2}+\frac{2}{7-3\sqrt{5}}-7\)
- step1: Reduce fractions to a common denominator:
\(\frac{\left(7-3\sqrt{5}\right)\left(7-3\sqrt{5}\right)}{2\left(7-3\sqrt{5}\right)}+\frac{2\times 2}{\left(7-3\sqrt{5}\right)\times 2}-\frac{7\left(14-6\sqrt{5}\right)}{14-6\sqrt{5}}\)
- step2: Calculate:
\(\frac{94-42\sqrt{5}}{14-6\sqrt{5}}+\frac{4}{14-6\sqrt{5}}-\frac{98-42\sqrt{5}}{14-6\sqrt{5}}\)
- step3: Transform the expression:
\(\frac{94-42\sqrt{5}+4-\left(98-42\sqrt{5}\right)}{14-6\sqrt{5}}\)
- step4: Remove the parentheses:
\(\frac{94-42\sqrt{5}+4-98+42\sqrt{5}}{14-6\sqrt{5}}\)
- step5: Calculate:
\(\frac{0}{14-6\sqrt{5}}\)
- step6: Calculate:
\(0\)
The value of \( x+\frac{1}{x}-7 \) is 0 when \( x=\frac{7-3\sqrt{5}}{2} \).
Similarly, when \( x=\frac{7+3\sqrt{5}}{2} \), the value of \( x+\frac{1}{x}-7 \) is also 0.
Therefore, the value of \( x+\frac{1}{x}-7 \) is 0 for both solutions of the equation \( x^{2}-7x+1=0 \).
Quick Answer
The value of \( x+\frac{1}{x}-7 \) is 0 for both solutions of the equation \( x^{2}-7x+1=0 \).
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