Find an example of an arithmetic sequence that has an explicit pattern. Then determine the formula for that sequence and use it to define the given term.

11)

5, -5, -15, -25,  ...

-5-5 = -10;   -15-(-5) = -10;   -25-(-15) = -10   ⇒  this is an example of arithmetic sequence that has explicit patern (evey next term is 10 less than previous one)

difference:  d = -10

first term:  a = 5

so the formula:

and:

12)

19, 26, 33, 40,  ...

26-19 = 7;   33-26 = 7;   40-33 = 7   ⇒  this is an example of arithmetic sequence that has explicit patern (evey next term is 7 more than previous one)

difference:  d = 7

first term:  a = 19

so the formula:

and:

13)

-20, -29, -38, -47,  ...

-29-(-20) = -9;   -38-(-28) = -9;   -47-(-38) = -9   ⇒  this is an example of arithmetic sequence that has explicit patern (evey next term is 9 less than previous one)

difference:  d = -9

first term:  a = -20

so the formula:

and:

11)

1, -2, 3, -4,  ...

-5-1 = -3;   3-(-2) = 5 ≠ -3   ⇒  this is NOT an example of arithmetic sequence

however it has explicit patern:

so:

180 square centimeters

step-by-step explanation:

1010: 3030

is it i think