д)(5х-с)(х-5с)=25х^2-25xc-xc+5cx=25х^2-26xc+5cx е)(4м+3n)(4м+3n)=(4m+3n)^2 или 16m^2+12mn+12mn+9n^2=16m^2+24mn+9n^2 ж)(3у-2v)(3у+2v)=9y^2-4v^2 з)(10х+3z)(10х-5z)=100x^2-50xz+30xz-15x^2=85x^2-20xz