Question

if a-b=4 and ab=21, find value of a3-b3? ans- 148 aana chaiye​

Answer 1

Given :-

a - b = 4

ab = 21

To Find :-

a³ - b³ = ?

Answer :-

- 188

Solution :-

a³ - b³

[ • Using identity ]

= ( a - b )³ - 3ab ( a - b )

[ • Now putting the values ]

= ( 4 )³ - 3 × 21 × 4

= 64 - 252

= - 188 [ • Required Answer ]

Answer 2

a-b=4(given).

and , a×b=21(given).

then the value of , a³--b³ is_'_________________

#a³--b³=(a--b)³ --3ab (a--b)

=(4)³ --3×21(4)

=64--252

= --188