1.find the twelfth element of an arithmetic sequence whose first term is 2 and second term element is 5?

2.find the first element of an arithmetic sequence whose eight element is 2 and common difference is -2?


Sagot :

[tex] t_{1} [/tex]
1.) Cannot be determined because an arithmetic sequence has to have 3 given terms, the given example has only 2.

2.) Arithmetic sequence formula:

[tex] t_{n} [/tex] = [tex] t_{1} [/tex] + (n-1)d

[tex] t_{8} [/tex] = [tex] t_{1} [/tex] + (8-1)-2

2 = [tex] t_{1} [/tex] + (7)-2

2 = [tex] t_{1} [/tex] + -14

2 + 14 = [tex] t_{1} [/tex] + -14 + 14

16      = [tex] t_{1} [/tex] + 0

16 = [tex] t_{1} [/tex] = 1st term


Answer: 16