If a + b + c = 2 and ab + bc + ca = -1, then the value of $a^3 + b^3 + c^3 -3abc $ is :
Answer & explanation
Correct answer: option 1
We know that,
If x + y = n
then, $x^3 + y^3$ = n3 - 3 × n × xy
If a + b + c = 2
ab + bc + ca = -1,
then the value of $a^3 + b^3 + c^3 -3abc $ = ?
If the number of equations are less than the number of variables then we can put the extra variables according to our choice =
So here two equations given and three variables are present so put c = 0
If a + b = 2
ab = -1,
then the value of $a^3 + b^3$ = 23 - 3 × 2 × -1 = 8 + 6 = 14