Step-by-step explanation:

1.) 5, -1, -7, ..

-1 = 5 + ( 2 - 1 ) d

-1 = 5 + d

-1 - 5 = d

-6 = d (common difference)

a_4 = 5 + ( 4 - 1 ) (-6)

a_4 = 5 + (3)(-6)

a_4 = 5 - 18

a _4 = -13

a_5 = 5 + ( 5 - 1 ) (-6)

a_5 = 5 - 24

a_5 = -19

Therefore: -13 and -19 are the next two terms

2. 4.1, 11.1, 18.1, ..

11.1 = 4.1 + ( 2 - 1 ) d

11.1 = 4.1 + d

11.1 - 4.1 = d

7 = d (common difference)

a_4 = 4.1 + ( 4 - 1 ) (7)

a_4 = 4.1 + 21

a_4 = 25.1

a_5 = 4.1 + ( 5 - 1 ) (7)

a_5 = 4.1 + 28

a_5 = 32.1

Therefore: 25.1 and 32.1 are the next two terms

3. -3x, -10x, -17x, ..

-10x = -3x + ( 2 - 1 ) d

-10x = -3x + d

-10x + 3x = d

-7x = d (common difference)

a_4 = -3x + ( 4 - 1 ) (-7x)

a_4 = -3x - 21x

a_4 = -24x

a_5 = -3x + ( 5 - 1 ) (-7x)

a_5 = -3x - 28x

a_5 = -31x

Therefore: -24x and -31x are the next two terms