Question

If 2a +b=12 and ab=15,then find the value of 8a^3 +b^3

Answer 1

Hey !!
Here is your answer !!
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▶ ( 2a + b )3 = (2a)3 + (b)3 + 3 (2a×b) ( 2a + b )
▶ ( 12 )3 = 8a3 + b3 + 3 ( 2ab ) ( 12)
▶ 1728 = 8a3 + b3 + 6 (ab) (12)
▶ 1728 = 8a3 + b3 + 6 (15 ) (12)
▶ 1728 = 8a3 + b3 + 90× 12
▶ 1728 = 8a3 + b3 + 1080
▶ 8a3 +b3 = 648
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Hope it helps u !☺☺

Answer 2

= ( 2a + b )3 = (2a)3 + (b)3 + 3 (2a×b) ( 2a + b )

=( 12 )3 = 8a3 + b3 + 3 ( 2ab ) ( 12)

=1728 = 8a3 + b3 + 6 (ab) (12)

=1728 = 8a3 + b3 + 6 (15 ) (12) =1728 = 8a3 + b3 + 90× 12

= 1728 = 8a3 + b3 + 1080

=8a3 +b3 = 648