If a + b + c = 2 and ab + bc + ca = -1, then the value of $a^3 + b^3 + c^3 -3abc $ is :

14

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