Consider the function. f(x) = -2x36x + 48x Step 1 of 2: Find all values of x that correspond to horizontal tangent lines. Select "None" if the function does not have any values of x that correspond to horizontal tangent lines. AnswerHow to enter your answer (opens in new window) 6 Points Separate multiple entries with commas. Keypad Keyboard Shortcuts Selecting a radio button will replace the entered answer value(s) with the radio button value. If the radio button is not selected, the entered answer is used. x = None