Draw a square in the coordinate system and divide it into 2 triangles
Find the area of one triangle
[tex]S=\frac{1}{2} ah\\h=2, a=4\\S=\frac{1}{2} *4*2=4[/tex]
The area of a square is the area of two triangles
[tex]S=2*4=8[/tex]
Answer: S=8
P.S. Hello from Russia and sorry for my bad english :)