Answer:
x² + 23x + 49
Explanation:
Area of the big rectangle
= (x + 10)(2x + 5)
= 2x² + 5x + 20x + 50
= 2x² + 25x + 50
Area of the small white rectangle
= (x + 1)(x + 1)
= x² + x + x + 1
= x² + 2x + 1
Area of the shaded area
= (2x² + 25x + 50) - (x² + 2x + 1)
= 2x² + 25x + 50 - x² - 2x - 1
= x² + 23x + 49