Question

expand 8x³ - 2✓2y³ + 81✓3z³ - 18✓6xyz​

Answer 1

x + y + z) ² = 100

x ² + y ² + z ² + 2 (xy + xz + yz) = 100--------------(1)

Now x ² + y ² + z ² = 38

implies xy + xz + yz = 31

or (xy + xz + yz) ² = (31) ²

using identity x ³ + y ³ + z ³ - 3xyz = (x + y + z) (x ² + y ² + z ²-xy -xz- yz)

= 10 × [38- 31]

= 70

Now x ³ + y ³ + z ³ = 160

or 160- 3xyz = 70

3xyz = 90

xyz = 30