Given #a_17=-82, d=-3#, how do you find #a_24#?

1 Answer
Mar 2, 2017

Answer:

#a_24 = -93#

Explanation:

Find the first element of the sequence using the formula for arithmetic sequences: #a_n = a_1 + (n-1)d#

#a_17 = -82 = a_1 + (17-1)(-3)#
#-82 = a_1 + 16(-3)#
#-82 = a_1 -48#
#-82+48 = a_1 -48+48#
#a_1 = -82 + 48#
#a_1 = -24#

Now use the arithmetic sequence formula to find #a_24#:

#a_24 = -24 + (24-1)(-3)#
#a_24 = -24 + (23)(-3)#
#a_24 = -24 -69#
#a_24 = -93#