Question

In the arithmetic sequence 20,16,12......a)find the common differents? b) how many positive are there in this sequence

Answer 1

Answer:

Common Difference,D="-4"

No. Of Positive Nos.="5"

Step-by-step explanation:

Using The Common Difference Formula:

$D=a_{2}-a_{1}=a_{3}-a_{2}\\\ D= 16-20=12-16\\\ D=-4$

Hence, D="4"

Using We came To know That The Last Positive No is 4.

Applying The Formula For A(n):

$a_{n}=a+(n-1)d$

$4=20+(n-1)(-4)\\\\\frac{4-20}{-4} =n-1\\\\\frac{-16}{-4} =n-1\\\\4=n-1\\\\n=4+1\\\\n=5$

Hence Total Postive Nos. Are "5"