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    				| 1. | Find the locus of a point such that the sum of itsdistance from the points (0, 2) and `(0,-2)`is 6. | 
| Answer» Let P(h,k) be any point on the locus and let A(0,2) and `B(0,-2)` be the given points. By the given condition. We get `PA+PB=6` or `sqrt((h-0)^2+(k-2)^2)+sqrt((h-0)^2+(k+2)^2)=6` or `sqrt(h^2+(k-2)^2)=6-sqrt((h-0)^2+(k+2)^2)` or `h^2+(k-2)^2=36-12sqrt(h^2+(k+2)^2)+h^2+(k+2)^2` or `-8k-36=-12sqrt(h^2+(k+2)^2)` `(2k+9)=3sqrt(h^2+(k+2)^2)` or `(2k+9)^2=9{h^2+(k+2)^2}` or `4k^2+36k+81=9h^2+9k^2+36k+36` or `9h^2+5k^2=45` Hence the locus of (h,k) is `9x^2+5y^2=45`. | |