The equation of a pair of straight lines is -
A x 2 + H y 2 + 2 G x y = 3 2
Where, A=Arithmetic mean of a & b, G=geometric mean of a & b, H=harmonic mean of a & b.(A and G = 0 )
If H = 2 ,
What is the distance between the Y-intercepts made by the two lines?
This is an original problem and belongs to my set Raju Bhai's creations
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Let a = b (Considering the equality case)
A = 2 2 a = a
G = a 2 = a
H = 2 a 2 a 2 = a
But given that H = 2
⟹ A = G = H = 2
Hence, the combined equation becomes 2 x 2 + 2 y 2 + 4 x y = 3 2 .
Which is the same as writing x 2 + y 2 + 2 x y = 1 6
⟹ ( x + y ) 2 = 1 6
⟹ ( x + y ) = ± 4
Therefore, the two separated equations are x + y = 4 and x + y = − 4 .
Clearly intercepts are ( 0 , 4 ) and ( 0 , − 4 ) .
Distance between them, d = 8
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A=Arithmetic mean of a & b, G=geometric mean of a & b, H=harmonic mean of a & b.
We know that , G = A H
Given equation,
⟹ A x 2 + H y 2 + 2 G x y = 3 2
⟹ A x 2 + H y 2 + 2 A H x y = 3 2 . …(because G = A H )
⟹ ( A x ) 2 + ( H y ) 2 + 2 A H x y = 3 2 ……… (this is in form of x 2 + y 2 + 2 x y = ( x + y ) 2 )
⟹ ( A x + H y ) 2 = 3 2
⟹ A x + H y = ± 3 2
⟹ y = − H A x ± H 3 2
This is in form of y = m x + c
So, the intercepts are + H 3 2 and − H 3 2
Given, H=2
Y- intercept points are (0,4) and (0,-4)
Distance between the intercepts is 8