Sequences???

Question

Look at the sequence below.
To get to the next term in the sequence,subtract 90 from the term before.

500 410 320 ......

Write the first two terms of the sequence that are less than zero.

Answer 1

start with 500 & subtrakt 90n, n=0, 1, 2, 3,...

for n=5, 500-450=50

for n=6, 500-540=-40

for n=7, 500-630  =-130