Find the tenth term and the sum of the first 21 term of the progression _10,_8,_6..
4 answers
I don't know
I don't know
impatient much?
Once is enough, thank you.
Repeated postings will not get faster or better responses.
Once is enough, thank you.
Repeated postings will not get faster or better responses.
By the "Just Look At It Theorem", I can see that your sequence is
11, 10, 9, 8, 7
where a = 11 and d = -1
Using the formulas for this ...
term(10) = a + 9d = 11 + 9(-1) = 2
sum(21) = (21/2)(2a + 20d)
= (21/2)(22 - 20)
= 21
11, 10, 9, 8, 7
where a = 11 and d = -1
Using the formulas for this ...
term(10) = a + 9d = 11 + 9(-1) = 2
sum(21) = (21/2)(2a + 20d)
= (21/2)(22 - 20)
= 21
2 answers