(7х-8)/(5х+5) + (4-5х)/(3х+3) =
= (7х-8)(3х+3)/(5х+5)(3х+3) + (4-5х)(5х+5)/(5х+5)(3х+3) =
= (21х²+21х-24х-24)/(5х+5)(3х+3) + (20х+20-25х²-25х)/(5х+5)(3х+3) =
= (21х²+21х-24х-24 + 20х+20-25х²-25х)/(5(х+1)*3(х+1)) =
= (-4х²-8х-4)/(15(х+1)²) = -4(х²+2х+1)/(15(х+1)²) = -4(х+1)² / (15(х+1)²) = -4/15,
то есть данное выражение не зависит от переменной х
= 2(x+y)+(x+y)(y-x) = (x+y)(2+y-x).
<span>x+0,5y=-2,
</span>0,5y=-x-2,
y=-2x-4.
k=-2, m=-4.
Cos5x=-1/2
5x=+-2π/3+2πn
x=+-2π/15+2πn/5,n∈z
3.sin²a+23+3.cos²a=3.sin²a+3.cos²a+23=
=3(sin²a+cos²a)+23=3.1+23=3+23=26