Ответ:\((x-2y+5)^2=x^2+4y^2+25-4xy+10x-20y\).\(\left(\frac12k+4m-5n\right)^2=\frac14k^2+16m^2+25n^2+4km-5kn-40mn\).\((2x+y-z+1)^2=4x^2+y^2+z^2+1+4xy-4xz+4x-2yz+2y-2z\).\((a^2+bc-3d+2)^2=a^4+b^2c^2+9d^2+4+2a^2bc-6a^2d+4a^2-6bcd+4bc-12d\).