Let ABC be a triangle. Let A be the point (1,2) , y = x be the perpendicular bisector AB and x - 2y +1 =0 be the angle bisector of ∠C. If the equation of BC is given by ax + by -5 =0, then the value of a + b is
A
4
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B
2
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C
3
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D
1
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Solution
The correct option is B 2 For triangle ABC : A(1,2) and B=(2,1) is the image in y = x.The image of A(1,2) in the ine x-2y+1 =0 is given by x−11=y−2−2=45
Hence, coordinates of point are (95,25)
Since, this point lie on BC, therefore the equation of BC is
3x - y -5 = 0 ⇒a+b=2