If the following system of equations is satisfied, find the product of all possible values of a .
a 2 + a b + b 2 = 3 1 a 2 − a b + b 2 = 4 3
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after substituting b in the first equation and multiplying by a^2,it is a four degree equation in a and simply the product of roots is constant term divided by coefficientof a^4...............so no need to calculate individual roots
why cant the value of a be in decimal, or irrational, or even imaginary?
Thats weird, why we need to multiply? Why the answer isn't 6?
i followed the same method!!
Please mention that only integral values of 'a' are to be considered...
Did it in the same manner to get the answer.
Hello, we get a 2 + b 2 2 a b = 3 7 = 1 2 so a + b = ± 5 .
a then satisfies a 2 − 5 a − 6 or a 2 + 5 a − 6 and by Vieta we have ( − 6 ) ( − 6 ) = 3 6
Solving the system of equations: Subtracting the first to the second equation gives 2ab = - 12 and ab = -6. This also implies that a^2 + b^2 = 37. Since ab = -6, then b = -6/a. a^2 + (36/a^2) = 37. Multiplying both sides by a^2 gives... a^4 + 36 = 37a^2 Solving for the roots gives a = 6, -6, 1, -1. Hence the product of the roots is 36.
Let a 2 + a b + b = 3 1 . . . . . . . ( 1 )
and a 2 + a b + b = 4 3 . . . . . . . ( 2 )
from . . . . . . . ( 2 )
b 2 = 4 3 + a b − a 2
substituting this into . . . . . . . ( 1 ) we get
a 2 + a b + 4 3 + a b − a 2 = 3 1
from which we get 2 a b = 1 2
a b = 6
the possible values of a are 3 , 2 , 6 a n d 1
and their product 3 × 2 × 6 × 1
gives the answer of 3 6
sorry guys 2 a b = − 1 2
a b = − 6
the possible values of a are 3 , 2 , 6 a n d 1 o r − 3 , − 2 , − 6 a n d − 1
a 2 + a b + b 2 = 3 1 , a 2 − a b + b 2 = 4 3 . Adding and subtracting these two equation we get 2 a 2 + 2 b 2 = 7 4 < = > a 2 + b 2 = 3 7 .......................(1)
2 a b = − 1 2 ................(2)
Now adding and subtracting the equations we get
( a + b ) 2 = 2 5 < = > ( a + b ) = ± 5
( a − b ) 2 = 4 9 < = > ( a − b ) = ± 7
Solving these equations we get a= 6 , − 6 , 1 , − 1
The product of all possible values of a is 3 6
Its weird that they don't give condition that a & b are integers
why cant the value of a be in decimal?
subtract equations and you get 2ab=-12 = ab=-6. so a= -6, a=-1, a=1, a=6 work (note that if you check -2,3 and 2,-3 they do not work). so multiply the a solutions and you get 36! (note: that is not a factorial sign, it's only a normal exclamation point)
We have two term a^2 + ab + b^2 = 31 and a^2 - ab + b^2 = 43
adding all term we have 2a^2 + 2b^2 = 74
<=> 2(a^2 + b^2) = 74
<=> a^2 + b^2 = 37
a^2 + ab + b^2 = 31 then ab = -6
a^2 - ab + b^2 = 43 then - ab = 6
we assume a is positive, because factor positive of 6 is {1, 2, 3, 6} and this product is even
then the product of a = 1 x 2 x 3 x 6 = 36
Bro first of all a =2 doesn't satisfy the eqn.. And a can be -ve as well.. And a comes out to be ± 6 and ± 1
a 2 + a b + b 2 = 3 1 − − − − − − − − − − − − − − − − − − − − − − e q ( 1 )
a 2 − a b + b 2 = 4 3 − − − − − − − − − − − − − − − − − − − − − − − e q ( 2 )
e q ( 1 ) − e q ( 2 ) ,
2 a b = − 1 2
and a b = − 6
S o , b = a − 6
e q ( 1 ) + e q ( 2 ) ,
2 ( a 2 + b 2 ) = 7 4
And, a 2 + b 2 = 3 7
a 2 + b 2 = 3 7 − − − − − − − − − − − − − − − − − − − e q ( 3 )
2 a b = − 1 2 − − − − − − − − − − − − − − − − − − − − − − − − − − − − − e q ( 4 )
e q ( 3 ) + e q ( 4 ) ,
a 2 + 2 a b + b 2 = 2 5
( a + b ) 2 = 2 5
( a + b ) = + 5 o r ( a + b ) = − 5
Since b = a − 6 ,
a − a 6 = + 5 and a − a 6 = − 5
a 2 − 6 = 5 a and a 2 − 6 = − 5 a
Solve the above equations and you'll get
a = 6 , − 6 , 1 , a n d − 1
Hence, product of all possible value is 36
I did by same way
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Adding both the equation..
a 2 + b 2 = 3 7
Subtracting both the equations...
a × b = − 6
a = b − 6
Substitutiong b in the first equation,
a 2 + a 2 3 6 = 3 7
Multiplying by a 2 ,
a 4 − 3 7 a 2 + 3 6 = 0
( a 2 − 3 6 ) ( a 2 − 1 ) = 0
a = 6 , − 6 , 1 , − 1
Multiplying the solutions, we get the answer as \boxed{36}