Question

Any line is affine. If it passes through zero, it is a subspace, hence also aconvex cone

Answer 1

In the textbook 'Convex Optimization by Boyd', the following statement is written:

Any line is affine. If it passes through zero, it is a subspace, hence also a convex cone.

I agree with the statements, "line is affine.", and "It is also a convex cone.". However, I cannot understand the above statement. Please let me know that statement.

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