Question

I NEED HELP PLEASE THANKS! :) Find the seventh partial sum of 13, 22, 31, 40, ...

Answer 1

Answer:

Step-by-step explanation:

Arithmetic sequence

First term a = 13

Common difference = 2nd term - first term

                                 = 22 - 13

                             d = 9

$a_{n}= a + (n-1)d\\\\a_{7}= 13 + 6*9$

   = 13 + 54

  = 67

Sum of 7 terms = $\frac{n}{2}(2a + (n-1)d)$

                         = $\frac{7}{2}(2*13+6*9)$

                         =$\frac{7}{2}(26+54)$

                          = $\frac{7}{2}*80$

                         = 7 *40

                          = 280

Answer 2

Answer:

280

Step-by-step explanation:

the 7th number is