"The diagonal of a rectangle produce by itself the same are as produced by it's length and breadth"-This is baudhayan Teorm. Compare it with the Pythagorus property
So here ABCD is a rectangle and BD is the hypotenuse.
BC and DC are the sides and yellow and voilet are the square on these sides.
And the greenish portion is square on the hypotenuse of the rectangle.
So by cut and paste method you will have to check that the yellow square and voilet square will overlap the green square.
If its overlap the green square then the pythgoras theorem is proved.
More detail about it will be taught to to later.