Would you teach me about the nuance of above two sentences in detail?

[He seems to be a vey old man. vs He seems a very old man.]

i read a book " the above sentences are different of nuance
as it adds "to be" or not. but i don't understand it well.
how can i get it? pls help me by your specific, good explaining ~

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i'm gonna ask one more questions about the usage of "seem-verb"

i read the below sentenses in a book for English grammer.
that book says like number1 is correct and 2 is wrong.
based on the rasson that "Verb-seem have complement for subjective
meaning.
so we have to add "to be" in number 2 for adding subjective mean because economic has the meaning of objectiviness.
if it is done, number 1 sentence is correct.

1. This book seems to be about economics.
2. This book seems about economics.
Is what that book wrote right or not?

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after all , the aim of my questions is for understanding the "to be" -usage or nuance.