решите 26;27 пожалуйста

26
2(sinx+cosx)+(sinx+cosx)=0
(sinx+cosx)(2+sinx+cosx)=0
sinx+cosx=0/cosx
tgx+1=0
tgx=-1
x=-/4+k,kz
2+sinxcosx=0
2cos(x/2)+2sin(x/2)+2sin(x/2)cos(x/2)+cos(x/2)-sin(x/2)=0
sin(x/2)+2sin(x/2)cos(x/2)+3cos(x/2)=0/cos(x/2)
tg(x/2)+2tg(x/2)+3=0
tg(x/2)=a
a+2a+3=0
D=4-12=-8lt;0 нет корней
Ответ D
27
(x+y)(x-y)(x+y)/[x(x+y)-y(x+y)]-((xy)+y)=
=(x+y)(x-y)(x+y)/(x+y)/(x-y)-((xy)+y)=
=(x+y)(x-y)/(x+y)(x-y)-((xy)+y)=
=(x-y)/(x-y)-((xy)+y)=(x-y)(x+(xy)+y)/(x-y)-((xy)+y)=
=x+(xy)+y-(xy)-y)x
x=64  64=4=16
Ответ В