A(5, 3), B(3, -2) are two fixed points, find the equation to the locus of a point P which moves so that the area of the triangle PAB is 9 units.

Key points to solve the problem:


Idea of distance formula- Distance between two points A(x1,y1) and B(x2,y2) is given by- AB =


Area of a ΔPQR – Let P(x1,y1) , Q(x2,y2) and R(x3,y3) be the 3 vertices of ΔPQR.


Ar(ΔPQR) =


How to approach: To find the locus of a point we first assume the coordinate of the point to be (h, k) and write a mathematical equation as per the conditions mentioned in the question and finally replace (h, k) with (x, y) to get the locus of the point.


Let the coordinates of a point whose locus is to be determined to be (h, k). Name the moving point to be C


Given the area of ΔABC = 9



According to question:


9 =


18=|-10-5k+3k-9+3h+2h|


|5h-2k-19|=18


5h-2k-19=18 or 5h-2k-19= -18


5h-2k-37=0 or 5h-2k-1=0


Replace (h,k) with (x,y)


Thus, locus of point is 5x-2y-37=0 or 5x-2y-1=0 …….ans


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