Strict Inequality for Fatou Given $f_n(x)=(n+1)x^n; x\in [0,1]$
I want to show $\int_{[0,1]}f<\liminf\int_{[0,1]}f_n$, where $f_n$ converges pointwise to $f$ almost everywhere on $[0,1]$.
I have found that $\liminf\int f_n = \int f +\liminf\int|f-f_n|$, but I'm not sure how to use this, and I don't even know what $f_n$ converges to here. Can someone hint me in the right direction?

HINT
Consider $a \in [0,1)$. The main crux is to compute $$\lim_{n \to \infty} (n+1)a^n$$
To compute the limit note that $a = \dfrac1{1+b}$ for some $b > 0$.
Hence, $$a^n = \dfrac1{(1+b)^n} < \dfrac1{\dfrac{n(n-1)}2 b^2}\,\,\,\,\,\,\,\,\, \text{(Why? Hint: Binomial theorem)}$$ Can you now compute $\lim_{n \to \infty} (n+1)a^n$?
HINT: $$\lim_{n \to \infty} (n+1)a^n < \lim_{n \to \infty} \dfrac{2n+2}{n(n-1) b^2} = ?$$
