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यदि 3x +2y = 20 व xy = 14/9 तब 27x3 + 8y3 का मान ज्ञात कीजिए। |
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Answer» 3x + 2y = 20 …………… (1) वर्ग करने पर 9x2 + 4y2 + 12xy = 400 9x2 +4y2 = 400 – 12xy 27x3 + 8y3 = (3x)3 + (2y)3 = (3x + 2y) (9x2 + 4y2 – 6xy) = (3x + 2y)(400 – 12xy – 6xy) = (3x + 2y)(400 – 18xy) = (20)( 400 – 18 ×14/9 = (20) (400 – 28) = (20) (372) = 7440 |
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