L1:3x-y+6=0 and L2:3x-y-4=0 are two parallel lines.The coordinates of A are(0,y)B(0,y),M(0,y).Ao係L1,Bo係L2,M o係a同b既之間.
(a)If L1 and L2 cut the y-axis at A and B erspectively,find the coordinates of A and B.
(b)If M is the mid-point of AB,find the coordinates of M.
(c)Find the equation of the lineL which is parallel to L1 and passes through point M.
Maths(Coordinate Treatment of Simple Locus Problems)
2007-04-06 8:36 pm
回答 (1)
2007-04-06 9:39 pm
✔ 最佳答案
(a)L1:3x-y+6=0 and L2:3x-y-4=0 cust the y-axis at A & B respectivelyFor L1:3x-y+6=0
put x=0, y = 6
therefore, the coordinates of A is (0, 6)
For L2:3x-y-4=0
put x=0, y = -4
therefore, the coordinates of B is (0, -4)
(b) M is the mid-point of AB, therefore, the coordinates of M is
( (0+0)/2, [6+(-4)]/2 ) = (0, 1)
(c) slope of L1 = 3, coordinates of M is (0,1), therefore the equation of the line L
(y-1)/(x-0) = 3
3x = y -1
3x-y +1 = 0
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