1 original ESAT Maths 1 coordinate geometry questions in the real exam style, each with a step-by-step worked solution and an explanation of why the tempting wrong answers are wrong. Try each one before opening the solution.
Methods on this page:Perpendicular bisector: equidistant from both points
Question 1ESAT Maths 1Standard
The perpendicular bisector of the line segment joining A(4,4) and B(−4,1) crosses the y-axis at (0,k). What is k?
A−25
B21
C23
D25
E27
F29
G211
Show the answer and worked solution
Answer: D · Method: Perpendicular bisector: equidistant from both points
The midpoint of AB is (0,25) and AB has gradient 83, so the bisector has gradient −38.
Alternatively: (0,k) is the same distance from A and B.