the third term of an arithmetic is 21, and the eigth term is 56. the first term is...

Question

anonymous · Answer

2 equations 
21=a+2d

56=a+7d

anonymous · Answer

use this for more reference . i am busy sorry contact me for help though ....XD http://openstudy.com/study#/updates/504cef62e4b02980ad8101c4

anonymous · Answer

the first term is 7

anonymous · Answer

@trina1478

anonymous · Answer

yes

solomonzelman · Answer

lets get a notation and everything I will denote (that all mathematicians denote) straight.

notation                  read as                    meaning

$\large\color{black}{ \displaystyle a_1  }$                            a of 1                      the first term
                                                                in a sequence

$\large\color{black}{ \displaystyle a_2  }$                            a of 2                      the second term
                                                                in a sequence

$\large\color{black}{ \displaystyle a_3  }$                            a of 3                      the third term
                                                                in a sequence

and so forth...
and IN GENERAL.


$\large\color{black}{ \displaystyle a_n  }$                            a of n                     any   $\rm n$ th   term
                                                                in a sequence

solomonzelman · Answer

Now, in arithmetic sequence, all terms follow a certain pattern.
You always add or subtract the same number to get to the next term.

We refer to this number that you add or subtract (in an arithmetic sequence, to get to the next term) using a letter "d"

(because it id the $\rm d$ifference  between the terms)

anonymous · Answer

gice me medal i answered correctly