Y=8x*ctgx
y`=8*ctgx-8x/sin²x
6х²-12ху+6у²=6(х²-2ху+у²)=6(х-у)²
1) 0,6-1,6x+6,4=21-1,2x
1,6x+1 ,2x=21-7
2,8x=14
x=5
n^2+7n+12=n^2+3n+4n+12=n(n+3)+4(n+3)=(n+3)(n+4),
2x(y+5)-z(y+5)=(y+5)(2x-z)
x=-0.7
y=4.04
z=-0.4
(4.04+5)(2*(-0.7)+0.4) = 9.04*(-1.4+0.4)=9.04*(-1)= -9.04