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If the orthocentre of the triangle f...

If the orthocentre of the triangle formed by the lines `2x + 3y -1 = 0, x +2y -1=0, ax + by -1=0` is at the origin then (a,b) is given by.

A

(6,4)

B

`(-3,3)`

C

`(-8,8)`

D

`(0,7)`

Text Solution

Verified by Experts

The correct Answer is:
C

The equation of a line through A i.e., the point of intersection of AB and AC is .
`(x + 2y -1)+lambda(2x + 3y -1) =0" "…..(i)`
If it passes through (0,0) then `-1- lambda = 0 rArr lambda = -1`
Substituting `lambda = - 1` in (i), we get
x + y =0 as the equation of AD.
Since `AD bot BC`. Therefore,
`-1 xx -(a)/(b) = - 1 rArr a+ b = 0" "....(ii)`
ltbr Similarly, by applying the condition that BO is perpendicular to CA, we get
` a + 2b = 8" "......(iii)`
Sloving (ii) and (iii), we get a =- 8, b = 8 .
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