Question

which term of an ap 84,80,76,72........ is first negative term

Answer 1

84,80,76,72.............

a=84

d= 80-84=-4
= 76-80=-4
= 72-76=-4

an = a+(n-1)d
=84+(n-1)-4
=84-4n+4
=84-4n

For the first negative term

= an < 0

= 84-4n <0

= 84 < 4n

= 84\4 < n

= 21 < n

The first negative term is 21st term.

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