a cube+ b cube= 0 then log(a+ b)-1/2(log a+ log b+ log3)
Answers
Question:-
a ³+ b ³= 0 then log(a+ b)-1/2(log a+ log b+ log3)
Answer:-
A³ +B³ =(A+B)(A² + B² -AB)=0.
as (A+B) can’t be zero, (A² + B² -AB)=0.
A² + B²=AB. …….1)
log(A+B)=0.5log((A+B)^2)=0.5log(A^2 + B^2 + 2AB)…..2)
FROM 1) AND 2)
Log(A+B)=0.5Log(3AB)…..3)
now,
logA + logB + log3=log(3AB)…..4)
using 3 and 4 you get your answer as zero.
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Hey Buddy
Here's The Answer
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Given :
a³ + b³ = 0
To find :
log ( a+b ) - 1/2 ( log a + log b + log 3 )
We know
=> log a + log b = log ( a.b)
=> log a - log b = log ( a/b )
Now
=> log ( a+b ) - 1/2 ( log ( a.b ) + log 3 )
=> log ( a+b ) - 1/2 ( log ( 3.a.b ) )
=> log ( a+b ) - log ( 3ab )¹´²
=> log ( a+b / √3ab ) ________ ( 1 )
Now
a³ + b³ = 0
=> ( a² + b² - ab ) ( a + b ) = 0
Now we have 2 cases
=> ( a + b ) = 0
If we put ( a + b = 0 ) in eq ( 1 ), the log will become 0, so it's can't be done.
=> ( a² + b² - ab ) = 0
=> a² + b² + 2ab - 2ab - ab = 0 ( modification )
=> ( a + b )² - 3ab = 0
=> ( a + b )² = 3ab
=> a + b = ( 3ab )¹´²
=> a + b = √ 3ab
Now putting value of ( a + b ) = √ 3ab in eq ( 1 )
=> log ( a+b / √3ab )
=> log ( √3ab / √3ab )
=> log 1
=> 0 ✓
Hope It Helps.