1 and "equal to" are generally conditional and need to meet certain conditions before they can be established.

2, and "identity" is unconditional and holds in any case.

3. So, if f(x) is always equal to X 2+X, whatever X is holds; And x 2+x cannot be said to be a constant equal to 0, because

This only holds true when x=0 or-1 Answer to supplementary questions: Generally speaking, there are two situations where "identity" will be used.

Yu ":First, when we need to emphasize; Second, not using "constant equals" will cause misunderstanding. For other situations.

"Equal to"

Mathematics [English: Mathematics, derived from the ancient Greek μ θ η μ α (má th ē ma); Often abbreviated as math or maths], it is a discipline that studies concepts such as quantity, structure, change, space and information.

Mathematics is a universal means for human beings to strictly describe the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence. In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.

Mathematics plays an irreplaceable role in the development of human history and social life, and it is also an indispensable basic tool for studying and studying modern science and technology.