Free help with homework

Why join Brainly?

  • ask questions about your assignment
  • get answers with explanations
  • find similar questions

The sum of first m terms of an AP is 4m 2 -m. if its n th term is 107, find the value of n. also find the 21 st term of this AP.



Given Sm=4m^2-m an=107---> a+(n-1)d=107 S1=4*1-1=3 S2=4*4-2=14 S2-S1=a2=11 a+d=11. [[[ d=8]]] a=11-d =11-8=3 a+8n=115. 3+8n=115. n=112/8=14 a21=a+20d = 3+20*8 =163
0 0 0
The Brain
  • The Brain
  • Helper
Not sure about the answer?
Learn more with Brainly!
Having trouble with your homework?
Get free help!
  • 80% of questions are answered in under 10 minutes
  • Answers come with explanations, so that you can learn
  • Answer quality is ensured by our experts