Asked by  | 15th Jan, 2010, 08:57: AM

Expert Answer:

We assume me mean PA + PB is minimum, if it's different please clarify.

Let the coordinates of point P be (x,y) = (x,x), since it lies on the line y = x.

PA + PB = f(x) =[(x-3)2+(x-4)2] + [(x-7)2+(x-13)2]

df(x)/dx = [2(x-3)+2(x-4)]/2[(x-3)2+(x-4)2] + 2(x-7)+2(x-13)/2[(x-7)2+(x-13)2] = 0

Solving for x, we can obtain the coordinates of P.




Answered by  | 15th Jan, 2010, 10:14: AM

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