Home » Aptitude » Elementary Algebra » Question
  1. If a + b + 1 = 0, then the value of (a3 + b3 + 1 – 3ab) is
    1. 3
    2. 0
    3. –1
    4. 1
Correct Option: B

As we know from the formula,
A3 + B3 + C3 = ( A + B + C) (A2 + B2 + C2 – AB – BC – CA) + 3ABC
If A + B + C = 0 then,
A3 + B3 + C3 = 0 x (A2 + B2 + B2 – AB – BC – CA) + 3ABC
A3 + B3 + C3 = 0 + 3ABC
A3 + B3 + C3 - 3ABC= 0
As we know that from given question,
A = a, B = b and C = 1, Put these value in above equation, we will get
a3 + b3 + 13 - 3 x a x b x 1 = 0
a3 + b3 + 1 - 3ab = 0



Your comments will be displayed only after manual approval.