10 questions · Form 4 Additional Mathematics Bab 7: Coordinate Geometry
The point P(k, 5) divides the line segment joining A(-1, 2) and B(7, 8) internally in the ratio m : n. Find the ratio m : n.
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. The point P(k, 5) divides the line segment joining A(-1, 2) and B(7, 8) internally in the ratio m : n. Find the ratio m : n.
Answer: A
Using y-coordinate: y = n y₁ + m y₂m + n => 5 = 2n + 8mm + n => 5m + 5n = 8m + 2n => 3n = 3m => mn = 11 => 1 : 1.
2. Find the equation of the locus of a moving point P(x, y) such that its distance from A(0, 3) is twice its distance from B(3, 0).
Answer: A
PA = 2 PB => PA² = 4 PB² => x² + (y - 3)² = 4[(x - 3)² + y²] => x² + y² - 6y + 9 = 4[x² - 6x + 9 + y²] => x² + y² - 6y + 9 = 4x² - 24x + 36 + 4y² => 3x² + 3y² - 24x + 6y + 27 = 0 (which simplifies to x² + y² - 8x + 2y + 9 = 0).
3. Find the coordinates of the point P that divides the line segment joining A(1, 2) and B(6, 12) internally in the ratio 2 : 3.
Answer: A
P(x, y) = (3(1) + 2(6)2 + 3, 3(2) + 2(12)2 + 3) = (3 + 125, 6 + 245) = (155, 305) = (3, 6).
4. The points A(1, 3), B(4, k), and C(7, 11) are collinear. Find the value of k.
Answer: A
Gradient AB = Gradient AC => k - 34 - 1 = 11 - 37 - 1 => k - 33 = 86 = 43 => k - 3 = 4 => k = 7.
5. The lines y = 2x + 1 and y = kx - 4 are perpendicular. Find the value of k.
Answer: A
m₁ = 2, m₂ = k. Since they are perpendicular, m₁ m₂ = -1 => 2k = -1 => k = -12.
6. Find the y-intercept of the line that is perpendicular to 4x - 2y + 5 = 0 and passes through (2, 1).
Answer: A
4x - 2y + 5 = 0 => 2y = 4x + 5 => y = 2x + 2.5, so m₁ = 2. Perpendicular gradient m₂ = -12. Line: y - 1 = -12(x - 2) => y = -12 x + 1 + 1 => y = -12 x + 2. The y-intercept is 2.
7. A moving point P(x, y) maintains a constant distance of 3 units from the line y = 2. What is the equation of the locus of P for y > 2?
Answer: A
The locus of points at distance 3 from horizontal line y = 2 consists of parallel lines y = 2 + 3 = 5 and y = 2 - 3 = -1. For y > 2, the equation is y = 5.
8. Find the perpendicular distance from the origin (0,0) to the midpoint of the line joining A(2, 6) and B(6, 2).
Answer: A
Midpoint M = (2+62, 6+22) = (4, 4). Distance OM = √(4² + 4²) = √32 = 4√2 units.
9. Calculate the area of the triangle with vertices A(1, 2), B(5, 3), and C(3, 7).
Answer: A
Area = 12 | (1)(3) + (5)(7) + (3)(2) - [ (2)(5) + (3)(3) + (7)(1) ] | = 12 | (3 + 35 + 6) - (10 + 9 + 7) | = 12 | 44 - 26 | = 12 (18) = 9 unit².
10. Three vertices of a parallelogram ABCD are A(1, 1), B(4, 2), and C(5, 6). Find the coordinates of vertex D.
Answer: A
In a parallelogram ABCD, midpoints of diagonals AC and BD coincide. Midpoint AC = (1+52, 1+62) = (3, 3.5). Let D = (x, y). Midpoint BD = (4+x2, 2+y2) = (3, 3.5). Thus 4 + x = 6 => x = 2; 2 + y = 7 => y = 5. So D = (2, 5).