Multiple choice

The equation of a circle is $x^{2}+y^{2}=25$, The equation of its chord whose middle point is $(1,-2)$ is given by:

  1. $x+2y+5=0$
  2. $2x-y+5=0$
  3. $x-2y-5=0$
  4. $2x+y+5=0$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The equation of a chord of a circle x^2 + y^2 = r^2 with midpoint (x1, y1) is T = S1, where T = xx1 + yy1 - r^2 and S1 = x1^2 + y1^2 - r^2. Here x1=1, y1=-2, r^2=25. x(1) + y(-2) - 25 = 1^2 + (-2)^2 - 25. x - 2y - 25 = 1 + 4 - 25. x - 2y - 25 = -20. x - 2y - 5 = 0.

Keep practicing — related questions