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If a--b = 4 and ab = 45, find the value of a3 - b3

Correct Answer: 604

Explanation:

( a     b ) 2   =   a 2   +   b 2   - 2 ab     16   =   a 2   +   b 2     90     a 2   +   b 2   =   106   a 3     b 3   =   ( a     b )   ( a 2   +   b 2   +   ab )     a 3     b 3   =   4   X   ( 106   +   45 )     a 3     b 3   =   4   X   151     a 3     b 3   =   604


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