Increasing decreasing Polynomial function

How do i do this activity, is appreciated

∆red ≅ ∆ by rule will give brainiest if possible

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm