If the nth term of arithmetic progression is, -1,4,9,14...............129. Find the value of n.

If the nth term of arithmetic progression is, -1,4,9,14...............

1.	If the nth term of arithmetic progression is, -1,4,9,14...............129. Find the value of n.
Answer» Use formula an =a+(n-1)×d129=-1+(n-1)×5130=5n-5 135÷5=n27=n Its 27 Ram here l is not 149 its 129 N=31 Here a=-1, d=4-(-1)=4+1=5 , l=149so 149=-1+(n-1)x5149=-1+5n-55n=149+6=155so\xa0{tex}\\begin{array}{l}n=\\frac{155}5=31\\\\\\end{array}{/tex}