The specified sign "*" represents an operation, that is, a * b = AB + A + B, a, B are positive real numbers, and 1 * k = 7 is known, then the range of function f (x) = k * x is______ | Math enthusiast | Mathematical art

The specified sign "" represents an operation, that is, a b = AB + A + B, a, B are positive real numbers, and 1 * k = 7 is known, then the range of function f (x) = k * x is______

∵ a * b = AB + A + B, ∵ 1 * k = K + 1 + k = 7, the solution is k = 4 or K = 9, the test shows that k = 9 does not conform to the meaning of the problem, ∵ k = 4, ∵ f (x) = k * x = 4x + 4 + X, ∵ x > 0, ∵ f (x) range is: (4, + ∞), so the answer is: (4, + ∞)

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