Identify the 42nd term of an arithmetic sequence where a1 = - 12 and a27 = 66

Question

Mathematics

Townsend

28 February, 08:30

Identify the 42nd term of an arithmetic sequence where a1 = - 12 and a27 = 66

+3

Answers (1)

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Lee Shepard · Answer 1

A1 = - 12

a2 = a1+d = - 12+d

a3 = a2+d = a1+2*d = - 12+2*d

...

a27 = a26+d = a1+26*d = - 12+26*d = 66

so: 26*d=66+12

26*d=78

d=78:26

d=3

therefore: a42 = a1+41*d = - 12+41*3 = - 12+123=111