a , b and c are real numbers such that a = b and a 2 ( b + c ) = b 2 ( a + c ) = 2 , find the value of c 2 ( a + b )
If
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Congratulations. A nice way of thinking.
What's with that kangaroo? :D
I just substituted a = b = c = 1 . Btw why is that kangaroo?
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It is given a is not equal to b.
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Yeah... Let a = 1 and b= 1 . 0 0 0 0 0 . . . . 0 1
It is just given to cancel off a − b as in @Angel Daniel Lopez Flores 's solution
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@Pranjal Jain – 1.00000....01 still has a limit of 1. Its like 0.99999...
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@Ryan McDaniel – I mean 1 can be approximated as 1 + 1 0 − 9 9 9 9 9 9 9 9 9 9
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@Pranjal Jain – I do not think that helps!
a 2 ( b + c ) = b 2 ( a + c ) = 2 a 2 ( b + c ) = b 2 ( a + c ) c ( a 2 − b 2 ) = a b ( b − a ) c ( a + b ) ( a − b ) = − a b ( a − b ) ( c ( a + b ) ) 2 = ( − a b ) 2 c 2 ( a + b ) = a + b a 2 b 2
From the original equations: c = a 2 2 − b = b 2 2 − a a − b = b 2 2 − a 2 2
a − b = 2 a 2 b 2 ( a + b ) ( a − b ) a + b a 2 b 2 = c 2 ( a + b ) = 2
Since
(a^2)( b + c ) = (b^2)( a + c )
Then
( a - b )( a b + a c + b c ) = 0 , but a, b are not equal, then
a b + a c + b c = 0
c( a + b ) = - a b
Multiply by c
Then
(c^2)( a + b ) = - a b c ......................... (1)
Since
(a^2)( b + c ) = (b^2)( a + c ) = 2
Then
a + c = 2/b^2
b + c = 2/a^2
eliminating c
Then
(2/b^2) - a = (2/a^2) - b
Simplifying , then we get
a + b = (a^2)(b^2)/2
multiply by c^2
Then
(c^2)( a + b ) =(a^2)(b^2)(c^2)/2 ...............(2)
From (1) , (2) we get
a b c = -2
substituting in (1) we get
(c^2)( a + b ) = 2
really a nice problem
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0 = a 2 ( b + c ) − b 2 ( a + c )
= a b ( a − b ) + ( a 2 − b 2 ) c
= ( a − b ) ( a b + a c + b c ) but a = b ,
then a b + a c + b c = 0 .
Multiplying by a − c
0 = ( a − c ) ( a b + a c + b c )
0 = a c ( a − c ) + ( a 2 − c 2 ) b
0 = a 2 ( b + c ) − c 2 ( a + b )
then c 2 ( a + b ) = a 2 ( b + c ) = b 2 ( a + c ) = 2