Answer: hx + ky = r².
- A hx + ky = r²
- B hx - ky = r²
- C x² + y² = r² + hk
- D h² + k² = r²
Correct answer: A. hx + ky = r²
Explanation: Using T=0 formula: replace x² by hx and y² by ky in the circle equation. This gives hx+ky=r² as the chord joining the two tangent-points from external point (h,k). Ans: hx+ky=r².
The slope of a line is the ratio of vertical change (rise) to horizontal change (run) between any two points on it - equivalently, the tangent of the angle θ the line makes with the positive x-axis.