(4х-у)²-(х+3у)²=(4х-у-х-3у)(4х-у+х+3у)=(3х-4у)(5х+2у)=15х²-20ху+6ху-8у²=
=15х²-8у²-14ху
(2^3*5)^(n+5) / (2^(3n+11) * 5^(n+4))=
2^(3n+15-3n-11) * 5^(n+5-n-4)=2^4 * 5= 16*5=80
Cos п/5*cos п/8=1/2сos(π/5-π/8)+1/2cos(π/5+π/8)=
=1/2cos3π/40+1/2cos13π/4<span>
Sin п/10*cos п/8=</span>1/2sin(π/5-π/8)+1/2sin(π/5+π/8)=
=1/2sin3π/40+1/2sin13π/4
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