यदि \(x^2-7x+r=0\) की जड़ें \(\alpha,\beta\) हैं और \(\alpha^2\beta+\alpha\beta^2=84\), तो (r) क्या है?
If \(\alpha,\beta\) are roots of \(x^2-7x+r=0\) and \(\alpha^2\beta+\alpha\beta^2=84\), what is (r)?
Explanation opens after your attempt
Correct Answer
B. (12)
Concept
We use (\alpha-2\beta+\alpha\beta-2=\alpha\beta\(\alpha+\beta\)). Here \(\alpha+\beta=7\), so (7r=84) and (r=12).
Why this answer is correct
The correct answer is B. (12). We use (\alpha-2\beta+\alpha\beta-2=\alpha\beta\(\alpha+\beta\)). Here \(\alpha+\beta=7\), so (7r=84) and (r=12).
Exam Tip
(\alpha-2\beta+\alpha\beta-2=\alpha\beta\(\alpha+\beta\)) होता है। यहाँ \(\alpha+\beta=7\), इसलिए (7r=84) और (r=12)।
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