<span>Xy^2+y+x^2y+x+4xy+4= (xy^2 + x^2y+ 4xy) + (y+x+4) =
=xy(y+x+4) + (y+x+4) = (x+y+4)*(xy+1).</span>
Дискриминант д.б. больше нуля
D=b^2-108>0
b^2>108
IbI>√108
b>√108 и b<-√108
Cos(pi/2+x) = -sinx
cos2x= cos^2x - sin^2x
-sinx = cos^2x - sin^2x
cos^2x =1 - sin^2x
-sinx = 1-sin^2x - sin^2x
2sin^2x - sinx - 1 =0
sinx = t
2t^2-t-1=0
D = 1 + 8 = 9
t1 = 1+3/4 = 4/4 = 1
t2 = -2/4 = -0.5
sinx = 1
x = pi/2+2pin
sinx = -0.5
x = -pi/6+2pin
x = -5pi/6+2pin
1) 9a²b²c³(3ac²-4b²)
2)8x∧7y∧5z²(2z-9y)
3)(10a-9b)(10a+9b)
4)2xy(3x-2y)(3x+2y) все)))