If x + y + z = 10 and xy + yz + zx = 15, then find the value of x3 + y3 + z3 - 3xyz .
Answer & explanation
Correct answer: option 3
If x + y + z = 10
xy + yz + zx = 15
then find the value of x3 + y3 + z3 - 3xyz = ?
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 z = 0
If x + y = 10
xy = 15
then find the value of x3 + y3 = ?
If x + y = n
then, $x^3 + y^3$ = n3 - 3 × n × xy
then, $x^3 + y^3$ = 103 - 3 × 10 × 15
$x^3 + y^3$ = 1000 - 450 = 550