${\left( -5 \right)}^{2}-{\left( 2 \times \left( -1 \right) \right)}^{2}$
Any expression multiplied by $-1$ equals its opposite${\left( -5 \right)}^{2}-{\left( -2 \right)}^{2}$
Evaluate the power$25-{\left( -2 \right)}^{2}$
Evaluate the power$25-4$
Subtract the numbers$21$