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If 5x – 4y = 7 and Xy = 8, Find : 125x3 – 64y3. - Mathematics

Sum

If 5x – 4y = 7 and xy = 8, find : 125x3 – 64y3.

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Solution

125x3 − 64y3 = (5x)3 − (4y)3

= (5x − 4y)3 + 3(5x) (4y) (5x − 4y)

= (5x − 4y)3 + 60xy (5x − 4y)

= (7)3 + 60 (8) (7)

= 343 + 3360

= 3703

Concept: Application of Formulae
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 12 Identities
Exercise 12 (D) | Q 15 | Page 155
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