a1, a5, a13 (terms of AP) are in GP and a6 + a15 =63. Find a23

• a1
  a5= a1+ 4d
  a13= a1+12d
  Now a5/a1 = a13/a5---->>a1=4d........(1)
  
  Given a6 + a15=63
  ----> a1+5d + a1+14d=63
  ---->2a1+ 19d = 63
  ---->8d+ 19d=63 from (1)
  ----> d=63/27= 7/3
  so a=4d=4*7/3=28/3 from (1)
  
  a23= a1+ 22d =28/3 +22*7/3
  =182/3
• 7 years agoHelpfull: Yes(14) No(1)
• (a13/a5)=(a5/a1),put a13=a+12d
  a5+a+4d and so on, we will get a=4d and same thing in another equation then value of d=7/3and a=28/3 and by putting the value a23=182/3
  
  
  
  
  
  
  
  
  
  
  
  
• 7 years agoHelpfull: Yes(2) No(0)