Question

Or
Q. If a - b = 4 and ab = 21, find the value of a3-b3.
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Answer 1

Required Answer :-

We have ,

• a - b = 4
• ab = 21

We need to find the value of a³ - b³ . Formula for (a - b)³ is given by ,

• (a - b)³ = a³ - b³ - 3ab(a - b)

Putting the given values in the identity ,

=> (4)³ = a³ - b³ - 3(21)(4)

=> 64 = a³ - b³ - 252

=> a³ - b³ = 252 + 64

=> a³ - b³ = 316

Therefore the value of a³ - b³ is 316.