130, - 12, 56.1, 11.2
these are all arithmetic sequences with n th term formula
[tex]a_{n}[/tex] = [tex]a_{1}[/tex] + (n - 1 )d
where d is the common difference and [tex]a_{1}[/tex] the first term
(1)
d = 10 - 4 = 4 - (- 2 ) = 6 and [tex]a_{1}[/tex] = - 14
[tex]a_{25}[/tex] = - 14 + (24 × 6) = - 14 + 144 = 130
(2)
d = 14 - 16 = 16 - 18 = - 2 and [tex]a_{1}[/tex] = 22
[tex]a_{18}[/tex] = 22 + (17 × - 2 ) = 22 - 34 = - 12
(3)
[tex]a_{50}[/tex] = 2.2 + (49 × 1.1) = 2.2 + 53.9 = 56.1
(4)
[tex]a_{12}[/tex] = - 4.2 + (11 × 1.4 ) = - 4.2 + 15.4 = 11.2
