1.

If 2x-y+1=0 is a tangent on the parabola which intersect its directrix at (1,3) and focus is (2,1), then equation of axis of parabola is

Answer»

`11x-2y=24`
`11x+2y+24=0`
`2x-11y-24=0`
`2y+11x=24`

Solution :`:'` Image of `(2,1)` in `2x-y+1=0` is
`(x-2)/2=(y-1)/(-1)=(-2(4-1+1))/(4+1)=(-8)/5`
`impliesx=2-16/5=(-6)/5`
`y=8/5+1=13/5`
`:.` Slope of DIRECTRIX `=(13/5-3)/((-6)/5-1)=(-2/5)/(-11/5)=2/11`
`:.` Equation of AXIS,
`=y=1=(-11)/2(x-2)`
`implies2y-2=-1x+22`
`implies11x+2y=24`


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