I need help with this, I'm not really understanding

Determine if the sequence is geometric. If it is, find the common ratio and the explicit formula. 19) -4, 20, -100, 500, ... 20) 1, 5, 25, 125, ... 21) -4, -8, -16, -32, ... 22 ) 2 , - 6, 18 , -54 , ... 23) 2, -8, 32, -128,... 24) 1 , -1 , - 3 , -5 ,... Determine if the sequence is geometric. If it is, find the common ratio and the recursive formula. 25) 3, 12, 48, 192, ... 26) -1, -4, -16, -64,... 27) 1, 6, 36, 216, ... 28) 4, 8, 16, 32, ... 29) -2, -4, -8, -16,... 30) 1, -6, 36, -216, ... Given the first term and the common ratio of a geometric sequence find the explicit formula and the recursive formula. 31) a = -2, r=-2 32) a = -4, r= 4 34) a = -1, r=2 33) a = -3, r=-2 36) a = 1, r=5 35) a =-3, r=3 -2