Question

Find the value of 8x^3+27y^3 if 2x+3y =13 and xy =6

Answer 1

Answer. Given : 2x+3y=13 and  xy=6...........(2)
              to find : the value of 8x3+27y3
 
=>2x+3y=13..............(1)
lets us cube both the sides
=>(2x+3y)3 = 133
  => (2x)3 + (3y)3 + 3 (2x) (3y) (2x + 3y) =2197 { applying the formula (a+b)3 =                                                                                        a3+b3 + 3ab( a+b ) }
=> 8x3 + 27 y3 + 18 xy(13)= 2197 ...............{using eq 1 value }
=> 8x3 + 27 y3 + 18 (6)(13)= 2197...............{using eq 2 value }
=>  8x3 + 27 y3 = 2197 - 1404
=>  8x3 + 27 y3 = 793 Answer 

Answer 2

i hope this helps you

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