Let a be a real number such that a3 - 3a2 + 27 = 0. Then the value of a7 + 486a2 is

738
2187
0
-2187

• 2187 is the answer.
  Just multiply the above equation by a^4
  we get, a7-3a6+27a4=0
  a7=3a6-27a4--------equation 1
  
  Now to find a6 multiply above equation by a^3
  we get, a6-3a5+27a3=0
  a6=3a5-27a3--------equation 2
  
  To find a6 multiply above equation by a^2
  we get, a5-3a4+27a2=0
  a5=3a4+27a2--------equation 3
  
  Now a7=3a6-27a4 from equation 1
  =3(3a5-27a3)-27a4 from equation 2
  =9a5-81a3-27a4
  =9(3a4-27a2)-81a3-27a4 from equation 3
  =27a4-243a2-81a3-27a4
  =-243a2-81a3
  =-243a2-81(3a2 -27) from the given equation
  a7 =-243a2-243a2+2187
  a7 =-486a2+2187
  
  So, a7 + 486a2 = 2187
• 11 years agoHelpfull: Yes(59) No(2)
• It means break it until and unless you don't come to the power of two. :)
• 11 years agoHelpfull: Yes(0) No(0)
• 2000+187aise ho hoga
• 11 years agoHelpfull: Yes(0) No(0)