Question

the 12th term of an ap is minus 28 and 18th term is minus 46 find its first term and common difference?

Answer 1

a'12 = -28 = a + (12 - 1)d = a + 11d
a'18 = -46 = a + (18 - 1)d = a + 17d
Subtracting first equation from the second, we get,
6d = - 18
d = -3
Hence,
a = -11d - 28
a = 33 - 28
a = 5
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Answer 2

here you go ☆☆

▪a12 = -28
▪a18 = -46

a + 17d = -46
a + 11d = -28
- - +
__________
6d = -18

d = -18/6

▪d = -3

a + 11×-3 = -28

a -33 = -28
a = -28 + 33
= 5


▪a = 5

AP = 5, -2.......