Answer:
Triangle DEF is reflected across x -axis.
Step-by-step explanation:
Since, the rule of reflection across x -axis,

The rule of reflection across y -axis,

The rule of reflection across line y = x,

The rule of reflection across y = -x ,

Since, in transformation of the triangle DEF with vertices D(-1,-1) , E(1,-1) and F(-1,-6) into the triangle D′E′F' with vertices D′(-1,1) , E′(1,1) , and F′(-1,6).
The rule of reflection is,

Thus, the triangle DEF is reflected across x -axis.