The correct options are
A f(x) is increasing in(0,∞)
C f(x)>e2x in (0,∞)
f′(x)−2f(x)>0 ∀ x∈R ⋯(1)
Let y=f(x)
Then dydx−2y>0
Integrating function I.F.=e∫−2dx=e−2x
Multiplying by e−2x, we get
e−2xdydx−2ye−2x>0
⇒ddx(y.e−2x)=ddx(f(x).e−2x)>0
Suppose g(x)=f(x).e−2x
Then g′(x)>0 ∀ x∈R [From (1)]
∴g(x)=f(x).e−2x is strictly increasing for all x∈R
Also, g(0)=1
⇒g(x)>g(0)=1 for all x>0
⇒f(x).e−2x>1 ∀ x∈(0,∞)
Hence f(x)>e2x ∀ x∈(0,∞)
As f′(x)>2f(x)⇒f′(x)>2e2x>2 ∀ x∈(0,∞)
∴f(x) is strictly increasing in (0,∞)