2ctgt+(1-ctgt)²=2ctgt+1-2ctgt+ctg²t=1+ctg²t=1/sin²t
(x-y)^2=x^2-2xy+y^2
(x+y)^2=x^2+2xy+y^2
x^2-y^2=(x-y)(x+y)
(x+y)^3=x^3+3x^2y+3xy^2+y^3
(x-y)^3=x^3-x^2y+3xy^2-y^3
x^3-y^3=(x-y)(x^2+xy+y^2)
x^3+y^3=(x+y)(x^2-xy+y^2)
А) 15a-3a+11a+5a-12a=16a
b) 3m-4n+5m+3n+n-7m=m
1) 1/6+(-4)+(-0,2)= 1-24-1,2= -24,2
-24,2*3=-72,6