It's going to be the top right picture
I’m not 100% sure but isn’t it x2 +xy +y2?
Check the picture below
surely you know how much that is.
There are 16 smaller triangles within the main large one. .25=1/4, so your fraction is 1/4. 1/4 of 16 is 4, because 4+4+4+4=16. So colour in 4 triangles. Hope this helps!