Which graph represents a reflection of f (x) = 1/10 (10) x across the y-axis?

The second one, B

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This is the concept of transformations, given the function given by f (x) = 1/10 (10) ^x, when the function is reflected along the y-axis the new function will be given by f (x) = 1/10 (10) ^ (-x). This will mirror the original function.