Let point A(a,0) is on x-axis and B (0,b) is on y-axis. 
Let P(h,k) divides AB in the ratio 1:2. So, by section formula h=1+22(0)+1(a)=3ak=32(b)+1(0)=32b⇒a=3h and b=23k Now, a2+b2=l2 ⇒9h2+49k2=l2⇒(3l)2h2+(32l)2k2=1 Now e=1−(9l2×4l29)=1−41=23 Thus, required locus of P is an ellipse with eccentricity 23.