# What is the minimum length to go grandmother's house taking water from river?

My home is $2m$ South from the river.If I go $12m$ straight to the West from my home and $1m$ straight to the South then I find my grandmother's house.What is the minimum length to go to grandmother's house taking water from river.
I can not understand what can I do with this problem.This is my homework.Please help me anyone

-
If the river bank is straight, then think about relflecting your house in it. – Henry Jan 9 '14 at 18:05

Assuming you don't know the "mirror trick", denote the point at which you take water from the river by $x$. Then the total distance is: $$y = \sqrt{2^2+x^2} + \sqrt{3^2+(12-x)^2}$$ Now, to find the minimum, find out when $dy/dx = 0$...