Apolygon with 21 sides as how many diagonals

answer:

171

step-by-step explanation:

generally the # of diagonals in sided polygon equals to : choose any two vertices out of to connect minus sides, which won't be diagonals. so, # of diagonals in 21 sided polygon is . since the diagonals from 1 particulat vertex shouldn't be counted then (one vertex makes diagonals). answer: 171.

i think it is everything has to equal 180 so, if i correct 4=c. 6=d. 8=a. 7=b. and the last question would be c. because they are parallel lines and they are congruent.

step-by-step explanation:

the reason everything has to equal to 180 is because that is how it works. i'm guessing that is its rule. 4 and 8 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 6 and 7 are congruent and parallel so, that would be 30+30 because they have the same number. it would equal 60. 60+60 is 180. so, now you have your answer

the answer is d

the answer is in the first quadrant, which make the y-int positive.

since the dots are going down, therefore the correlation is negative

i hope it is right.