alg2\trig
posted by dianela on .
if a3= 17 & a8=37 are terms in annarithmetic sequece, fina a1 & d. the answer is a1=9 & d=4 but i don't understand how they got the answer, please help!

term(3) = a + 2d (by definition)
= 17
term(8) = a + 7d = 37
a+7d = 37
a+2d = 17
subtract them
5d = 20
d = 4
sub into a + 2d=17
a + 8 = 17
d = 9