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## #1 2018-04-02 02:48:31

Monox D. I-Fly
Member
From: Indonesia
Registered: 2015-12-02
Posts: 1,379

### [ASK] Tangent of a Circle (Again)

If the line x + my = 1 is a tangent of the circle

, the value of m is ....
A. -2
B.

C.

D. 3
E. 4

Looking at the circle's equation, the center is (2, -3) and the radius is

. If I know the coordinate where the line meet the circle I think I can solve this by myself, but I don't know how. Should I substitute x = 1 - my to the circle equation, or is there a simpler way?

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away. May his adventurous soul rest in peace at heaven.

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## #2 2018-04-02 05:20:36

Alg Num Theory
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Registered: 2017-11-24
Posts: 342
Website

### Re: [ASK] Tangent of a Circle (Again)

Substitute x = 1 − my into the quadratic expression. If the line is tangent to the circle, this should be a perfect square. Complete the square (or otherwise) and solve for m.

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## #3 2018-04-02 05:57:47

Alg Num Theory
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Registered: 2017-11-24
Posts: 342
Website

### Re: [ASK] Tangent of a Circle (Again)

I got two values of m:

– neither of which is among your multiple choices. Are you sure you haven’t made a typo copying the question?

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## #4 2018-04-02 12:55:55

Monox D. I-Fly
Member
From: Indonesia
Registered: 2015-12-02
Posts: 1,379

### Re: [ASK] Tangent of a Circle (Again)

Yes, D should be 2 so that is the answer. Thanks.

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away. May his adventurous soul rest in peace at heaven.

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