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標題: help [打印本頁]

作者: abcdefg111 時間: 09-3-28 05:27 PM 標題: help

Find the equations of the tangents to 4x^2 + 9y^2=36 which pass through the point.(3,-3)
SORRY,打漏左

[ 本帖最後由 abcdefg111 於 2009-3-28 11:04 PM 編輯 ]

作者: 98102257 時間: 09-3-28 09:41 PM

pass through 咩 point ? 係唔係打漏左

作者: Naozumi 時間: 09-3-28 09:42 PM

pass through ?? point??

用 y = mx + c,代番個point得出m同c的係

再代 y = mx + c 入 4x^2 + 9y^2=36
咁就得得 quadratic equation in x
再用 discriminant = 0解番個 m

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