Question

Laaast one.

Find the sum.
(I've attached the equation below)

Thank you in advance!

Answer 1

What do you think it may be?

Answer 2

I'm honestly not sure, I don't know how to do these equations.

Answer 3

plug n = 1 and again n = 90
in the equation (3n - 7)
u will get the first and last term

Answer 4

and after tht u can get the sum easily

Answer 5

Okay. Working on paper and on my calculator I keep getting 11790. But it says it's wrong, so what am I doing wrong?

a1 = 3(1)-7=-1
an = 3(90)-7 =
s90 = 90/2(-1 + 263)
= 45(262)
= 11790

Answer 6

3(1) -7 = 3-7 = -4

Answer 7

I'm sorry, I still don't understand.

Answer 8

the first term, a1
we put n =1

3(1) - 7 = 3-7 = -(7-3) = -4
you have written that as -1

Answer 9

So instead, would it be 11831?

Answer 10

45(-4+263) = 45 (259) = 11655

how did u get 11831?

Answer 11

I did everything, except add the 45 at the front. That's what I got wrong.

Answer 12

So I did, (-4+263) = 45 (259) = 11831. But I see why that's wrong now. Is that all I do? :)

Answer 13

yes, the sum is 11655, thats it :)

Answer 14

Okie dokie, thank you so much for helping! And thanks for being patient lol.

Answer 15

no problem, welcome ^_^