1.

The equation of that chord of hyperbola `25x^(2)-16y = 400`, whose mid point is (5,3) isA. `115x - 117y = 17`B. `125x - 48y = 481`C. `127x + 33y = 341`D. `15x - 121y = 105`

Answer» Correct Answer - B
`S = 25 x^(2) - 16 y^(2) - 400 = 0`
Equation of required chord is `S_(1) =T` (i)
Here, `S_(1) = 25(5)^(2) - 16(3)^(2) - 400`
`= 625 - 144 - 400 = 81`
and `T = 25 xx_(1) - 16 yy_(1) - 400`, where `x_(1) = 5, y_(1) =3`
`= 25(x)(5) - 16(y)(3) -400 - 125 x - 48y - 400`
so from (i), required chord is
`125x - 48y - 400 = 81`
or `125x - 48y = 481`


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