if (p+q)=3 then what is the value of (p3 + q3 ), when it is given that p=1/q?
a. 123 b. 143 c. 111 d. 132

• (p+q)^3 = p^3 +q^3+3pq(p+q)
  p^3 +q^3 = (p+q)^3 - 3pq(p+q)
  =27-3(3)
  = 18
• 8 years agoHelpfull: Yes(28) No(3)
• (p+q)^3=p^3+q^3+3p^2q+3pq^2
  (3)^3=p^3+q^3+3(pq)p+3(pq)q
  Since p=1/q we get pq=1
  27=p^3+q^3+3p+3q
  27=p^3+q^3+3(p+q)
  27=p^3+q^3+3(3)
  27-9=p^3+q^3
  18=p^3+q^3
  Ans:18
  But i don't know the correct answer.Admin please verify it.
• 8 years agoHelpfull: Yes(9) No(2)
• p+q=3
  p^3+q^3= [p+q][p sq -pq + q sq]
  = 3[p sq-1 + q sq]
  =3[(p+q)^2- 2pq+1]
  =3[3^2 - 2 +1]
  =3[9-2+1]
  =24
  
  =
• 8 years agoHelpfull: Yes(3) No(3)
• p+q=3and p=1/q=>(q+1/q)=3
  (q+1/q)(q+1/q)=3*3
  =q^2+1/q^2+2=9
  q^3+1/q^3=24
  p=1/q=>p^3+1/q^3=24
  
• 8 years agoHelpfull: Yes(2) No(0)
• 18 is correct answer but options are wrong
• 8 years agoHelpfull: Yes(0) No(0)
• 18 is crct answer
• 8 years agoHelpfull: Yes(0) No(0)
• 18 will be the ans
  
• 8 years agoHelpfull: Yes(0) No(0)
• 18. Iz correct answer
• 8 years agoHelpfull: Yes(0) No(0)
• p+q=3
  P=1/q
  sub p=1/q
  (1/q)+q=3
  (1+q^2)/q=3
  1+q^2=3q
  q^2-3q+1=0
  to find root
  q=(3+or-(9-4*1*1)^(1/2))/2(1)
  q=(3+-2.236)/2
  q=2.3
• 7 years agoHelpfull: Yes(0) No(1)