1.

Find the equation for the ellipse that satisfies the givenconditions:Major axis on the xaxis and passes through the points (4, 3) and(6, 2).

Answer» Since the major axis of the ellipse lies on the x-axis, so it is a horizontal ellipse.
Let the required equation of the ellipse be
`x^(2)/a^(2) +y^(2)/b^(2) = 1" "("where "a^(2) gt b^(2))." "` …(i)
Since (4, 3) lies on (i), we have `16/a^(2) +9/b^(2) = 1." "` ...(ii)
Also, since (6, 2) lies on (i) , we have `36/a^(2) + 4/b^(2) = 1." "`...(iii)
Putting ` 1/a^(2) = u and 1/b^(2) = v ` in (ii) and (iii), we get
`16u+9v=1" "`...(iv)
`36u+4v=1" " ` ...(v)
On multiplying (iv) by 9 and (v) by 4, and subtracting, we get
` 65v = 5 hArr v = 1/13 hArr 1/b^(2) = 1/13 hArr b^(2) = 13.`
Putting ` v = 1/13 ` in (iv), we get
` 16 u = (1-9/13) hArr 16u = 4/13 hArr u = (4/13 xx 1/16) = 1/52 hArr 1/a^(2) = 1/52 hArr a^(2) = 52.`
Thus, `a^(2) 52 and b^(2) = 13.`
Hence, the required equation is `x^(2)/52 + y^(2)/13 = 1.`


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