Difficulty: Hard
Correct Answer: x = 7; y = -7
Explanation:
Introduction / Context:
This coordinate geometry question tests the section formula (also called the internal division formula). When a point divides a line segment joining two points in a given ratio m:n internally, its coordinates are a weighted average of the endpoints. Here, the endpoints are on the axes: A is on the X-axis at (x, 0) and B is on the Y-axis at (0, y). The dividing point P is given as (5, -2). Using the internal section formula separately for x-coordinate and y-coordinate gives two equations, allowing us to solve for x and y exactly.
Given Data / Assumptions:
Concept / Approach:
Internal division (section) formula:
If P divides A(x1, y1) and B(x2, y2) in ratio m:n internally, then:
Px = (m*x2 + n*x1) / (m + n)
Py = (m*y2 + n*y1) / (m + n)
Here m = 2, n = 5, A = (x, 0) and B = (0, y). Substitute and solve the two equations:
5 = (2*0 + 5*x)/7 and -2 = (2*y + 5*0)/7.
Step-by-Step Solution:
1) Identify values:
A(x1, y1) = (x, 0), B(x2, y2) = (0, y), m = 2, n = 5
2) Apply section formula for x-coordinate:
Px = (m*x2 + n*x1)/(m + n) = (2*0 + 5*x)/7 = 5
3) Solve for x:
(5x)/7 = 5
5x = 35
x = 7
4) Apply section formula for y-coordinate:
Py = (m*y2 + n*y1)/(m + n) = (2*y + 5*0)/7 = -2
5) Solve for y:
(2y)/7 = -2
2y = -14
y = -7
6) Therefore:
x = 7 and y = -7
Verification / Alternative check:
With x = 7 and y = -7:
A = (7, 0), B = (0, -7).
Compute P using formula:
Px = (2*0 + 5*7)/7 = 35/7 = 5,
Py = (2*(-7) + 5*0)/7 = -14/7 = -2.
It matches P(5, -2), confirming correctness.
Why Other Options Are Wrong:
• Any option with x = -7 would give Px = (5*(-7))/7 = -5, not +5.
• Any option with y = +7 would give Py = (2*(7))/7 = 2, not -2.
• x = ±3 values fail the x-coordinate equation immediately.
Common Pitfalls:
• Reversing the weights m and n in the section formula.
• Using external division formula by mistake (signs change there).
• Forgetting that A is (x, 0) and B is (0, y), so one coordinate is already zero at each endpoint.
Final Answer:
x = 7; y = -7
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