Practicing Success
If x + y + z = 2 xy + yz + zx = -11, then Find x3 + y3 + z3 - 3xyz. |
74 75 76 77 |
74 |
Here three variables and two eq. are given. Put z = 0 x + y = 2 xy = -11 find, ⇒ x3 + y3 + z3 - 3xyz = x3 + y3 + 0 - 0 = x3 + y3 ⇒ (x + y)3 = x3 + y3 + 3xy (x + y) ⇒ 8 = x3 + y3 + 3 × -11 (2) ⇒ x3 + y3 = 74 Note → If the number of given variables are more than the number of given equations then put all extra variables anything except \(\frac{1}{0}\) or \(\frac{0}{0}\) form. |