1. write the nth term of the following sequence in terms of the first term of the sequence. 10, 20, 40, . . 2.write the nth term of the following sequence in terms of the first term of the sequence. 2, -4, 8, -16, . . 3. write the nth term of the following sequence in terms of the first term of the sequence. a, a + 4, a + 8, .