0.0000024 in scientific notation

anyone? find the second, fifth, and ninth terms of a sequence where the first term is 65 and the common difference is -7. 72, 93, 121 72, 79, 86 58, 37, 9 58, 51, 44

What are the constants in this expression? -10.6+9/10+2/5m-2.4n+3m

Given the sequence 7, 14, 28, 56, which expression shown would give the tenth term? a. 7^10 b. 7·2^10 c. 7·2^9