1.

Find the equation of the set of all points whosedistances from (0,4) are `2/3`of their distances from the line `y=9.`

Answer» `(sqrt((h-0)^2+(k-4)^2))^2=(2/3|(k-9)/sqrt(1^2)|)^2`
taking root both side
`h^2+(k-4)^2=4/9((k-9)^2/1)`
`9h^2=9(k-4)^2=4(k-9)^2`
`9h^2+9k^2+144-72k=4k^2+324-72k`
`9h^2+9k^2-4k^2+144-324=0`
`9h^2+5k^2=180`
`(9h^2)/180+(5k^2)/180=1`
`h^2/20+k^2/36=1`
putting x=h,y=k
`x^2/20+y^2/36=1`.


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