If a + b + c = 7 and ab + bc + ca = -6, then the value of a³ + b³ + c³ − 3abc is:

469

If x + y  = n

then, $x^3 + y^3$ = n³ - 3 × n × xy

If a + b + c = 7

ab + bc + ca = -6

Then the value of a³ + b³ + c³ − 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 = 7

ab  = -6

Then the value of a³ + b³ = 7³ - 3 × 7 × -6

a³ + b³ = 469