Find the polynomial for the area.
The area is

 ¹/₂( x² - 10y² + 10xy - xy )

Step-by-step explanation:

From the diagram area of the triangle = ¹/₂ ˣ base ˣ height

where the base = x + 10y and the height = x - y

Therefore putting these into the formula above

Area  =   ¹/₂ [( x + 10y )( x -y )]

         =   ¹/₂( x² - xy + 10xy - 10y²)units²

         = ¹/₂( x² - 10y² + 10xy - xy )

i believe it's a.

i'm not sure on this one, most likely correct.