Answer :

To solve the expression [tex]\( 3xy(x^2 - xy + y^2) \)[/tex] with [tex]\( x = 1 \)[/tex] and [tex]\( y = -1 \)[/tex], let's break it down into detailed steps:

1. Substitute [tex]\( x = 1 \)[/tex] and [tex]\( y = -1 \)[/tex] into the expression:

[tex]\( 3 \cdot 1 \cdot (-1) \left(1^2 - 1 \cdot (-1) + (-1)^2\right) \)[/tex]

2. Simplify inside the parentheses first:
- Calculate [tex]\( x^2 \)[/tex]:
[tex]\[ 1^2 = 1 \][/tex]
- Calculate [tex]\( xy \)[/tex]:
[tex]\[ 1 \cdot (-1) = -1 \][/tex]
- Calculate [tex]\( y^2 \)[/tex]:
[tex]\[ (-1)^2 = 1 \][/tex]

Substitute these values back into the parentheses:
[tex]\[ 1 - (-1) + 1 \][/tex]

3. Simplify the expression inside the parentheses:
[tex]\[ 1 + 1 + 1 = 3 \][/tex]

4. Substitute back and simplify the overall expression:
[tex]\[ 3 \cdot 1 \cdot (-1) \cdot 3 \][/tex]

5. Further simplify the expression:
- First multiply [tex]\( 3 \cdot 1 \)[/tex]:
[tex]\[ 3 \][/tex]
- Then multiply [tex]\( 3 \cdot (-1) \)[/tex]:
[tex]\[ -3 \][/tex]
- Finally, multiply [tex]\( -3 \cdot 3 \)[/tex]:
[tex]\[ -9 \][/tex]

So, the value of the expression [tex]\( 3xy(x^2 - xy + y^2) \)[/tex] when [tex]\( x = 1 \)[/tex] and [tex]\( y = -1 \)[/tex] is [tex]\( \boxed{-9} \)[/tex].