The wire of length a is folded into a rectangle, the analytic expression of rectangular area y with respect to side length x is obtained, and the domain of definition of this function is written out If the length of one side is x, the length of the other side is (a-2x) / 2 So the area is y = x (a-2x) / 2 What is the definition field (0, a / 2)? If the side length is equal to 0, then the area is equal to 0, OK

The wire of length a is folded into a rectangle, the analytic expression of rectangular area y with respect to side length x is obtained, and the domain of definition of this function is written out If the length of one side is x, the length of the other side is (a-2x) / 2 So the area is y = x (a-2x) / 2 What is the definition field (0, a / 2)? If the side length is equal to 0, then the area is equal to 0, OK

First of all, starting from the requirements of the topic, it must be folded into a rectangle, so there must be an edge, so to satisfy x > 0 and (a-2x) > 0, we can find that if the edge of the domain is 0, there will be no so-called rectangle

There is a square 30 cm long on one side. If the length of the square increases by x cm, then the functional relationship between the increased value of area y square cm and the increased value of side length x cm is

The original area of the square is 900, which is increased to (30 + x) ^ 2,
So y = (30 + x) ^ 2-900
That is y = x ^ 2 + 60x