Question

Find S20 when t1 = 4 and d = 5

Answer 1

Now you have to use formula

Answer 2

tn=t1+(n-1)d

Answer 3

\(S_{n}=\frac{n}{2} (2 t_1 + (n-1)d)\)
sub n=20, and everything you've got there.
do u need further help?

Answer 4

cool

Answer 5

S(20=20/2(2(4)+(20-1)5)

Answer 6

And how would I work this out @Shadowys

Answer 7

um,simplify this then.
\(\frac{20}{2}[(2)(4)+(20-1)5]=10[8+19(5)]\)
what follows can be done by manual arithmetic or a calculator.

Answer 8

I got 1030

Answer 9

yup, that's what I got too. :)

Answer 10

Cool