Use the difference an+1 - an to show that the given sequence ( a,, ) is strictly increasing or strictly decreasing. n 8n - 71 =1 O : strictly decreasing (8n - 7)(8n + 7) O 7 (8n - 7)(8n + 1) strictly increasing O 7 strictly decreasing (8n + 7)(8n - 1) O 7 : strictly increasing (8n + 7)(8n - 1) O 7 (8n - 7)(8n + 1) ; strictly decreasing