text: # If 3x – 4y = 5 and Xy = 3, Find : 27x3 – 64y3. - Mathematics
  
  Sum
  
  If 3x – 4y = 5 and xy = 3, find : 27x3 – 64y3.
  
  #### Solution
  
  27x3 – 64x3 = (3x)3 – (4y)3
  
  = (3x − 4y)3 (3x − 4y)3 + 3 (3x) (4y) (3x − 4y) ......[ ∵ a3 − b3 = (a − b)3 + 3ab(a − b)]
  
  = (5)3 + 36(xy) (3x − 4y)
  
  = 125 + 36 (3) (5)
  
  = 125 + 540
  
  = 665
  
  Concept: Application of Formulae
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  #### APPEARS IN
  
  Selina Concise Mathematics Class 8 ICSE
  Chapter 12 Identities
  Exercise 12 (D) | Q 12 | Page 155
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