Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 1,238

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.

**Online**

**Alg Num Theory****Member**- Registered: 2017-11-24
- Posts: 298
- Website

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*.

Offline

**Alg Num Theory****Member**- Registered: 2017-11-24
- Posts: 298
- Website

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?

Offline

**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 1,238

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.

**Online**

Pages: **1**