[tex]2(x-y)(x+y)-3(x+2y)^2+(x-y)^2=[/tex]
[tex]2(x^2-y^2)-3(x^2+4xy+4y^2)+x^2-2xy+y^2=[/tex]
[tex]2x^2-2y^2-3x^2-12xy-12y^2+x^2-2xy+y^2=[/tex]
[tex]- 14xy - 13y^2[/tex]
[tex]-14\cdot \sqrt{2}\cdot \frac{ \sqrt{2} }{2}-13\cdot ( \frac{ \sqrt{2} }{2} )^2 =-14-13\cdot \frac{1}{2}=-14-6,5=-20,5[/tex]
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[tex]( \sqrt{2} x - 1)( \sqrt{2} x +1)-( \sqrt{2} x -1)^2+(x - \sqrt{2} )^2=[/tex]
[tex]2x^2-1-(2x^2-2 \sqrt{2}x+1)+x^2-2 \sqrt{2}x+2=[/tex]
[tex]2x^2-1-2x^2+2 \sqrt{2}x-1+x^2-2 \sqrt{2}x+2=[/tex]
[tex]x^2[/tex]
[tex](- \sqrt{3})^2=3[/tex]
