3-7х=11,
-7х=11-3,
-7х=7,
х=-1
(1/2*х-3у²)²=(1/2*х)²-2*1/2*3*ху²+(3у)²=1/4*х² -3 ху²+9у^4
a=-3
mx^2+nx^2+4m+4n+4mx+4nx=x^2(m+n)+4(m+n)+4x(m+n)=(m+n)(x^2+4x+4)=(m+n)(x+2)^2
А) [3х/(3х-у)] - [х/(3х+у)] - [2ху/(9х^2-у^2)]=
={[3х(3х+у)]/[(3х-у)(3х+у)]} - {[х(3х-у)]/[(3х-у)(3х+у)]}-{2ху/(3х-у)(3х+у)}=
=[9х^2+3ху-3х^2+ху-2ху]/(3х-у)(3х+у)=
=(6х^2-2ху)/(3х-у)(3х+у)=
=(2х(3х-у))/(3х-у)(3х+у)=2х/(3х+у)
б) (9-6а)/(а^3-27) - (а-3)/(а^2+3а+9)=
=(9-6а)/(а-3)(а^2+3а+9) - (а-3)/(а^2+3а+9)=
=(9-6а-а^2+6а-9)/(а-3)(а^2+3а+9)=
=-а^2/(а^3-27)=а^2/(27-а^3)