Question -
Answer -
Given f (x) = x9 + 4x7 + 11
Now by differentiating above equation with respect to x, we get
⇒ 
⇒ f’(x)= 9x8 + 28x6
⇒ f’(x)= x6(9x2 + 28)
As given x ϵ R
⇒ x6 >0 and 9x2 + 28 > 0
⇒ x6 (9x2 +28) > 0
⇒ f’(x)> 0
Hence, condition for f(x) to be increasing
Thus f(x) is increasing on interval x ∈ R