1.

यदि 3x +2y = 20 व xy = 14/9  तब 27x3 + 8y3 का मान ज्ञात कीजिए।

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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