[tex]a)\\\\2(3-x)(3+x)-(1-2x)^2+(2x+3)^2=\\2(9-x^2)-(1-4x+4x^2)+(4x^2+12x+9)=\\18-2x^2-1+4x-4x^2+4x^2+12x+9=\\-2x^2-4x^2+4x^2+4x+12x+18-1+9=\\-2x^2+16x+26[/tex]
[tex]b)\\\\(x+2y)^2-(y-2x)^2=\\x^2+4xy+4y^2-(y^2-4xy+4x^2)=\\x^2+4xy+4y^2-y^2+4xy-4x^2=\\-4x^2+x^2+4xy+4xy+4y^2-y^2=\\-3x^2+8xy+3y^2[/tex]
[tex]c)\\\\(\sqrt3-2\sqrt6)^2+12\sqrt2=\\(\sqrt3)^2-2*2\sqrt6*\sqrt3+(2\sqrt6)^2+12\sqrt2=\\3-4\sqrt{18}+24+12\sqrt2=\\27-12\sqrt{2}+12\sqrt2=27[/tex]
