If x + y + z = 7, xy + yz + zx = 8, then what is the value of $x^3+y^3+z^3-3 x y z$ ?
Answer & explanation
Correct answer: option 4
If x + y + z = 7
xy + yz + zx = 8
$x^3+y^3+z^3-3 x y z$ = ?
If the number of equation is less then the number of variables then we can put the extra variables according to our choice.
Here the number of variables are 3 and the number of equations are two than put z = 0
x + y = 7
xy = 8
x3+y3 = 73 - 3 × 7 × 8 = 343 - 168 = 175