f(x) = 2x3 + 18x2+54x +57 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. Answer Keypad How to enter your answer (opens in new window) Keyboard Shortcuts Separate multiple entries with commas. 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 5:17 PM 2/20/2022 home end insert delete prt sc DII F8 F9 F10 F11 F12 esc X F3 F4 F5 E6 F7 F1 F2 backspace a 4 O 7 B P Y U O E R tab W H K lock A S G