The function .
It is a identity function is a special case of the direct variation function.
The function in which the constant is 1.
The graph passes through all points with coordinates (a, a).
The function is a direct variation function.
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. is a special case of the direct variation function.![\"graph](\"/userfiles/image/Library/Algebra%202/graph%20of%20the%20function%20y=%20x.gif\")
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is a direct variation function.