Find the sum of the arithmetic sequence. 3, 5, 7, 9, 21

Given the arithmetic sequence

3, 5, 7, 9, ..., 21

The first term a = 3 & a common difference d = 5 - 3 = 7 - 5 = ... = 2

If there are n number of terms in the above A.P. then last term l = 21 will be the nth term given as:

l = a + (n - 1)d

21 = 3 + (n − 1)2

n = 10

Hence the sum of given arithmetic progression (A. P.) up to 10 terms is given general formula.

Sn = n/2(a + l)

S10 = 10/2(3 + 21)

= 120

a) y = -3x +2

b) y = 1/2x -6

these 2 can be combined into one equation.

-3x +2 = .5x -6

8 = 3.5x

x = 8 / 3.5 = 2.2857142857

y = -3 * (8 / 3.5) +2

y = (-24 / 3.5) + 2

y = -4.8571428571

step-by-step explanation: