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, . . .

  1. Write the nth term of the following sequence in terms of the first term of the sequence.

a, a + 4, a + 8, . . .