Question

What expression defines the artmetric series
15+25+35+... for seven terms?

Answer 1

as we can see 25-15=35-25=10(common difference)its an arithmetic series
a,the first term=15,so
7th term,a7=15+(7-1)*10
=15+60
=75

Answer 2

sum to 7th term,
S7 =(7/2)*(a7+a)=(0.5)*(75+15)*7=(0.5)*(630)=315

Answer 3

So the would be

Answer 4

Nice job!

Answer 5

thanks