If a2+b2-4(a+b)= -8,then the value of (a-b) is:

A. 4 B. 0 C. 2 D. 8

• ANS. B. 0
  EXPLANATION
  (a^2 -4a + 4) + (b^2 - 4b + 4) - 8 = -8
  (a-2)^2 + (b-2)^2 = 0
  Sum of two squares will be zero only when both of them are zero.
  So a-2 =0, b-2 = 0,
  a=2 and b=2
  and (a-b)=0
• 6 years agoHelpfull: Yes(8) No(1)
• Ans.assume value a=2 and b=2
  a-b =0
• 6 years agoHelpfull: Yes(5) No(3)
• a^2 +b^2 -4(a+b)=-8
  or a^2+b^2-4a-4b+8=0
  or a^2 +b^2-4a-4b+4+4=0
  or a^2-4a+4 +b^2-4b+4=0
  or (a-2)^2 +(b-2)^2=0
  
  From here a=2 b=2 proved
• 6 years agoHelpfull: Yes(3) No(0)
• Pallabhi .... here square is given...not multiplication by 2.
• 6 years agoHelpfull: Yes(1) No(0)
• I am not getting the point ... how can I directly assume it ? please specify
• 6 years agoHelpfull: Yes(1) No(0)
• A.4
  a2+b2-4(a+b)= -8
  2a+2b-4a-4b=-8
  -2a-2b=-8
  2(-a-b)=-8
  2(-3-1)=-8
  so a-b=4
• 6 years agoHelpfull: Yes(0) No(10)