which of the following is true? help ASAP

Question

a.) 2+7+12+...+(5n-4)=5n(n-1)/2  

b.)2+7+12+...+(5n-2)=5n(n-1)/2

c.)2+7+12+...+(5n-1)=n(5n-1)/2

d.)2+7+12+...+(5n-3)=n(5n-1)2

Answer 1

Brianna,

 

Choice d is correct.

 

Substitute n =1 and check.

Also verify for n = 2 and n = 3