यदि \(x=\sqrt{2}+\sqrt{5}\), तो \(x^{3}-7x\) का मान क्या है?
If \(x=\sqrt{2}+\sqrt{5}\), what is the value of \(x^{3}-7x\)?
Explanation opens after your attempt
A. \(10\sqrt{2}+4\sqrt{5}\)
Concept
Here \(x^{2}=7+2\sqrt{10}\), so \(x^{3}=17\sqrt{2}+11\sqrt{5}\) and \(x^{3}-7x=10\sqrt{2}+4\sqrt{5}\). In exams, first find \(x^{2}\) and then multiply by (x).
Why this answer is correct
The correct answer is A. \(10\sqrt{2}+4\sqrt{5}\). Here \(x^{2}=7+2\sqrt{10}\), so \(x^{3}=17\sqrt{2}+11\sqrt{5}\) and \(x^{3}-7x=10\sqrt{2}+4\sqrt{5}\). In exams, first find \(x^{2}\) and then multiply by (x).
Exam Tip
\(x^{2}=7+2\sqrt{10}\), इसलिए \(x^{3}=17\sqrt{2}+11\sqrt{5}\) और \(x^{3}-7x=10\sqrt{2}+4\sqrt{5}\)। परीक्षा में पहले \(x^{2}\) निकालकर फिर (x) से गुणा करें।
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