Plot[{0.3(Sin[x]+x Log[x] + 0.2),Sin[x]+x + 0.2}, {x, 0.01, 10},Filling->{1->{2}}, FillingStyle -> {Red, Blue}]

Plot[{Sin[x]+x Log[x] + 0.2,Sin[x]+x + 0.2}, {x, 0.01, 10},Filling->{1->{2}}, FillingStyle -> {Red, Blue}]

f∈O (g) ⧦ 
∃K>0, ∃(Subscript[n, 0])∈N, ∀n≥(Subscript[n, 0,]) f(n)≤k×g(n)

Plot[{2Sin[x]+x Log[x] + 0.5,x Log[x] + 0.5}, {x, 0.01, 8},Filling->{1->{2}}, FillingStyle -> {Red, Blue}]

Plot[{2Sin[x]+x Log[x] + 0.5,1.5(x Log[x] + 0.5),0.7(x Log[x] + 0.5)}, {x, 0.01, 8},Filling->{1->{2},1-> {3}}, FillingStyle -> {Red, Blue}]

f∈Θ(g) ⧦ 
∃(Subscript[k, 1])>0, ∃(Subscript[k, 2])>0, ∃(Subscript[n, 0])∈N, ∀ n≥(Subscript[n, 0,]) (Subscript[k, 1])×g(n)≤f(n)≤(Subscript[k, 2])×g(n)