1. (х+у)(x+y) = (x+y)^2
2. (p-g)(p-g) = (p-g)^2
3. (a+6)^2
1) 6ab
2) 12ac
3) 6a^2b
4) 75b^2c
5) 6(a+b)^4
6) 15(x+y)^5
7) 60(x-y)^3
8) 24(a-b)^4
Y^2+2y-4y-8-(y^2-4y+4)=y^2+2y-4y-8-y^2+4y-4=2y-4=2(y-2)
Sin20°+sin(90-77)sin57°-sin(90-57)sin77°=
sin20°+cos77°sin57°-cos57°sin77°=sin20°+sin57°*cos77°-cos57°*sin77°=sin20°+sin(57°-77°)=sin20°-sin20°=0