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Maths help please

a circle has the equation x^2+y^2+2x-6y+5=0

show that y = -1/2 is a tangent to the circle at the point (-2,1)

plz help me, I worked out the equation of the circle:
(x-1)^2 + (y-3)^2 = 5
Original post by Mya_oty
a circle has the equation x^2+y^2+2x-6y+5=0

show that y = -1/2 is a tangent to the circle at the point (-2,1)

plz help me, I worked out the equation of the circle:
(x-1)^2 + (y-3)^2 = 5


Should be (x+1)^2 instead.

Also, that line is not tangent to the circle. Please check the question.

EDIT: I assume you meant y=−12xy=-\frac{1}{2}x, in which case, substitute it into the circle's equation and show that it has a single root.
(edited 6 years ago)
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Mya_oty
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Original post by RDKGames
Should be (x+1)^2 instead.

Also, that line is not tangent to the circle. Please check the question.

EDIT: I assume you meant y=−12xy=-\frac{1}{2}x, in which case, substitute it into the circle's equation and show that it has a single root.


Do.I sub it into y=MX+c ??
Original post by Mya_oty
Do.I sub it into y=MX+c ??


No. You are looking to show something about the amount of intersections between a line and a circle.

So you sub the line into the circle.

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