Practicing Success
If $a + b + c = 19, ab + bc + ca = 120$, then what is the value of $a^3 + b^3 + c^3 - 3abc$? |
18 23 31 19 |
19 |
If $a + b + c = 19 ab + bc + ca = 120$ Then what is 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 $a + b = 19 ab = 120$ Then what is the value of $a^3 + b^3 $? If x + y = n then, $x^3 + y^3$ = n3 - 3 × n × xy $a^3 + b^3 $ = 193 - 3 × 19 × 120 $a^3 + b^3 $ = 6859 - 6840 = 19 |