1.

If `y= 3x+c` is a tangent to the circle `x^2+y^2-2x-4y-5=0` , then `c` is equal to :A. `(-2, 3)`B. `(4, -1)`C. `(2, -3)`D. `(4, 1)`

Answer» Correct Answer - A::D
Equation of given circle `x^(2) + y^(2) - 2x - 4y - 5 = 0`
`rArr (x-1)^(2) + (y - 2)^(2) = 0`
Equation of tangent `y = 3x + c`
Length of the perpendicular from centre `=` radius
`|(3-2+c)/(sqrt(3^(2)+1^(2)))| = sqrt(10) rArr c = 9.-11`
If `c = 9` then point of contact is `(-2,3)`
if `c = -11` then point of contact is `(4, 1)`


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