if a + b is 12 and ab is 27 then find a3+b3
priyal666666:
let a = 9 and b = 3,than a+b=12 that is 9+3=12 , a×b= 27 that is 9×3= 27. , now 3a+3b= 36 that is 3×3+3×9=9+27=36
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Answer :-
__________________________
• Given :-
a + b = 12
ab = 27
• To find :-
a³ + b³
• Salutation :-
[ Method - ( i ) ]
a³ + b³
= ( a + b )³ - 3ab ( a + b ) [ • Using identity ]
= ( 12 )³ - 3 × 27 × 12 [ • As given , ( a + b ) = 12 , ab = 27 ]
= 1728 - 972
= 756 [ • Required answer ]
Side note :-
• Used identity → ( a³ + b³ ) = ( a + b )³ - 3ab ( a + b )
___________________________
[ Method - ( ii ) ]
Let , a = 9 and b = 3
As , ( a + b ) = ( 9 + 3 ) = 12
And , ab = ( 9 × 3 ) = 27
Now ,
a³ + b³
= ( 9 )³ + ( 3 )³
= 729 + 27
= 756 [ • Required answer ]
____________________________
★ Be Brainly ★
__________________________
• Given :-
a + b = 12
ab = 27
• To find :-
a³ + b³
• Salutation :-
[ Method - ( i ) ]
a³ + b³
= ( a + b )³ - 3ab ( a + b ) [ • Using identity ]
= ( 12 )³ - 3 × 27 × 12 [ • As given , ( a + b ) = 12 , ab = 27 ]
= 1728 - 972
= 756 [ • Required answer ]
Side note :-
• Used identity → ( a³ + b³ ) = ( a + b )³ - 3ab ( a + b )
___________________________
[ Method - ( ii ) ]
Let , a = 9 and b = 3
As , ( a + b ) = ( 9 + 3 ) = 12
And , ab = ( 9 × 3 ) = 27
Now ,
a³ + b³
= ( 9 )³ + ( 3 )³
= 729 + 27
= 756 [ • Required answer ]
____________________________
★ Be Brainly ★
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