Given: <p> $X$ - any Banach space <br>$F : X \to X$ (linear bounded and non-invertible) <br>$P_n$, which is projector that strongly converges to the identity operator $I$ as $n \to\infty$ </p> Can you help me come up with a linear bounded and non-invertible operator $F$ such that the conditions are satisfied: $P_nFP_n$ - invertible on $ImP_n$<br> $\|(P_nFP_n)^{-1} \| < C$ (some constant)<br> $P_n \to I$ strongly If you can help at least with idea it also will be great. Thank you very much! If you think that such example doesn't exist: please can you prove it or help with idea of proving it. I've tried a lot of things. I'm already desperate, I really hope for your help, thanks.