Question

1.which term of the AP 45,41,37,33............ is the first negative term? 2.find the 10th term from the end to begining of the AP 4.9,14........254 3.find the 11th term from the end of the AP 10,7,4.....-64 4.the sum of first n terms of AP is given by n+8n.find its 12th term 5.find the sum of n terms of the AP a,a+d,a+2d.......a+(n-1)d.

Answer 1

Common difference=-4 Let nth be the first negative term anth<0 a+(n-1)d<0 45+(n-1)(-4)<0 (n-1)(-4)<-45 (n-1)4>45 4n-4>45 4n>49 n>49/4 n>12.25 Therefore 13th term is the first negative term of this AP