<span>|у+2|=7
у=7-2
у=5
-у+2=7
у=-9</span>
1+ctg2x=-1/sin2x
sin2x/sin2x + cos2x/sin2x + 1/ sin2x =0
sin2x+cos2x+1=0
cos^2 x - sin^2 x +2 sinxcosx+ cos^2x + sin^2x=0
2sinxcosx+2cos^2x=0
2cosx(sinx+1)=0
cosx=0
x=П/2 +Пn
sinx=-1
x= -- П/2 +Пn
( 4Y / ( Y^2 - X^2) ) - 2 / ( Y - X ) = ( 4Y - 2* ( Y + X )) / ( Y^2 - X^2 ) =
= ( 2Y - X) / ( Y^2 - X^2 )