the diagram shows two joint rectangles. The total area of the compound shape is 36cm

By algebraic approach we find that the compound shape is represented by the equation 2 · x² - 5 · x - 18 = 0 and the length of the line segment AB is 4.5 units.
The total area of the compound shape is the sum of the areas of the two rectangles, whose entire expression is:
A = x · (x - 4) + 2 · x · (x - 2) (1)
Then, we proceed to expand this expression by algebraic means:
A = x² - 4 · x + 3 · x² - 6 · x
A = 4 · x² - 10 · x
4 · x² - 10 · x - 36 = 0
2 · x² - 5 · x - 18 = 0
We need to solve the quadratic equation to determine the possible values of line segment AB. Please notice that lengths are nonzero positive integers:
2 · x² - 5 · x - 18 = 0
(x - 4.5) · (x + 2) = 0
There is only possibility for the length of the line segment AB: x = 4.5.
To learn more on quadratic functions: https://brainly.com/question/5975436
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