У=8 => 8=-3х+5
3х=5-8
3х=-3
х=-1
Получается 18х^20/9х^20=2
<span>3а(a-2)-(a-3)^2=
=3a^2-6a-(a^2-6a+9)=
=3a^2-6a-a^2+6a-9=
=2a^2-9</span>
2а+3-1.5а+0.5=(2а-1.5а)+(3+0.5)=0.5а+3.5
при а=-3
0.5а+3.5=0.5*(-3)+3.5=-1.5+3.5=2
при а=0
0.5а+3.5=0.5*0+3.5=0+3.5=3.5
при а=4
0.5а+3.5=0.5*4+3.5=2+3.5=5.5