What is the value of r if the distance between ... - JAMB Mathematics 2009 Question
What is the value of r if the distance between the points (4,2) and (1, r) is 3 units?
A
1
B
2
C
3
D
4
correct option: b
Applying the formula
(x - a)2 + (y - b)2 = r2
(4 - 1)2 + (2 - r)2 = (3)2
(3)2 + (2 - r)2 = (3)2
9 + ( 4 - 4r + r2) = 9
13 - 4r + r2 = 9
r2 - 4r + 13 - 9 = 0
(r2 - 2r) - (2r + 4) = 0
r(r - 2) -2(r - 2) = 0
(r - 2) (r - 2)
r = 2 or -2
(x - a)2 + (y - b)2 = r2
(4 - 1)2 + (2 - r)2 = (3)2
(3)2 + (2 - r)2 = (3)2
9 + ( 4 - 4r + r2) = 9
13 - 4r + r2 = 9
r2 - 4r + 13 - 9 = 0
(r2 - 2r) - (2r + 4) = 0
r(r - 2) -2(r - 2) = 0
(r - 2) (r - 2)
r = 2 or -2
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