The 80 cm long iron wire forms a rectangular frame, so that one side of the rectangle is x long and the area is y. find the functional relationship between Y and X and determine the definition

The 80 cm long iron wire forms a rectangular frame, so that one side of the rectangle is x long and the area is y. find the functional relationship between Y and X and determine the definition

Y = x times (40-x) = the square of 40x-x

Given that the area of a rectangle is 16 square centimeters, the functional relationship between the length of one side of the rectangle y (CM) and the length of the other side x (CM) is__ ,（①）
Supplement: the value range of independent variable x is___ .(②)
Let's get out of here..

X+Y=16
1≤X≤16

If the circumference of a rectangle is 12 and one side is x, then the other side is y. The analytic function of X is
The value range of the independent variable is

Perimeter = 2 (x + y) = 12
y=-x+6
X and y are both positive numbers
y=-x+6>0
x

It is known that the circumference of the rectangle is 10cm, one side is xcm, and the other side is YCM,
It is known that the circumference of the rectangle is 10cm, the length of one side is xcm, and the length of the other side is YCM!

2x+2y=10
That is, x + y = 5 (0