is (a*b) positive?
a) (a+b)^2 < (a-b)^2
b) (a+b)^3 < (a-b)^3

• only (a) is sufficient alone but cannot be answered with the help of other
  
  a) (a+b)^2 < (a-b)^2
  => (a+b)^2 - (a-b)^2 < 0
  => a*b < 0
  
  b) (a+b)^3 < (a-b)^3
  => 2b*(3a^2+b^2) < 0
  => b < 0
  we can't tell about a*b without knowing about a .
• 9 years agoHelpfull: Yes(26) No(3)
• either of the 1 statement is required
• 9 years agoHelpfull: Yes(2) No(1)
• from statement a it is clear that...a*b is negative....and from 2 we can conclude that.a*b may be positive so either of the statement can lead to the result
• 9 years agoHelpfull: Yes(1) No(0)
• Yes,(a+b)^2-(a-b)^20; Hence ab>0 mean a*b is positive .same apply fir b option.
  
• 9 years agoHelpfull: Yes(1) No(3)
• a or b anyone one of them can be negative but not both in first case so
  a) a*b is negative
  
  a and b both can be negative and only b can be negative
  b) a*b is positive or a*b is negative
• 9 years agoHelpfull: Yes(1) No(1)
• since (a+b)^2 - (a-b)^2= 4ab
  from option a) (a+b)^2 - (a-b)^2 < 0
  so 4ab < 0
  => ab < 0
  from option b) (a+b)^3 - (a-b)^3 b < 0 ; but we cant comment about the value of a. a can be either positive or negative. so correspondingly ab can be negative or positive.
  
  so only option (a) is sufficient to answer alone but cannot be answered with the help of other
• 9 years agoHelpfull: Yes(1) No(0)
• Only option (a) can be sufficient to find a*b as we can determine if a^2+b^2+2*a*b a^3+b^3+3*a*b(a+b) we cannot knoow a*b as we don't have values of a and b each from equation.So second option cannot be used to determne a*b
• 9 years agoHelpfull: Yes(0) No(0)
• only option a is sufficient.and b is not sufficient
• 9 years agoHelpfull: Yes(0) No(0)
• mr rakesh,for a) a*b
• 9 years agoHelpfull: Yes(0) No(0)