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

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

Sum

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

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Application of Formulae

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Chapter 12: Identities - Exercise 12 (D) [Page 155]

Chapter 12 Identities
Exercise 12 (D) | Q 15 | Page 155

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