15 . Which option is correct? Show work please

Question 15 Identify the open intervals on which the function ) = 10x - 20cosx, 0 -x - 2/f is increasing or decreasing 7 TL 5 TT 5 IT 1 1 76 increasing on 6 6 and 6 : 2 7t ; decreasing on 6 increasing on on (0 7 ) and ( " 2 7) decreasing on ing on (0. and 6 2 7 decreasing on 6" O 1 1 7 7 It increasing on | 0. and 6 . 2 71 : decreasing on |0. 6 7 TI 11 1 11 17 increasing on 6 6 :decreasing on | 0 6 and 6 , 2 TT