А

It looks like this is a math exercise involving algebraic expressions and equations. The tasks seem to involve simplifying or solving equations. Let's break down what each part could involve:

1. \( a) \, a^2 - 4b = \)

   • This seems to involve simplifying or evaluating the expression for given values of \( a \) and \( b \).

2. \( b) \, 2x + 2y = \)

   • This expression can likely be simplified or evaluated similar to the first expression.

If you need help solving or simplifying these expressions, please provide more context or specific instructions.