1)фи(x) = f(x)+g(x)
фи(3) = f(3)+g(3) = 1+9 = 10
фи(1) = f(1)+f(1) = 5+1 = 6
2)r(x) = f(x)•g(x)
r(2) = f(2)•g(2) = 3•4 = 12
r(4) = f(4)•g(4) = -1•16 = -16
X+y=81
x-y=15
x=81-y
81-y-y=15
x=81-y
-2y=-66
x=81-y
y=33
x=48
5пи/12=между 6пи/12=пи/2 и 4пи/12 = пи/3
илиточнее надо ?