Find all negative terms of the arithmetic sequence for which the nth term = 20n-78.

-58, - 38, - 18

Step-by-step explanation:

if for the nth term, the value is 20n-78, then for the 1st term, the value will be 20 (1) - 78

So we just need to use this formula for every term, starting from the 1st, until the value is no longer negative

20 (1) - 78 = 20-78 = - 58

20 (2) - 78 = 40-78 = - 38

20 (3) - 78 = 60-78 = - 18

20 (4) - 78 = 80-78 = 2

so those are the only negative terms

cya at RSM today