tangent

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If ax+by+c=0 is a tangent to xy=4, then find the sign of a and c .

#Mathematics #Co-ordinate Geometry

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aditya ravichandran ·2011-05-14 10:56:03

This equation :
ax+4bx+c=0
must have repeated roots ,so that it becomes tangent

ax²+cx+4b=0
c²-16ab=0

ab â‰¥0

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