Question

задания с подобными
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Answer 1

6.

$y - x - z = \\ (ab + c) - (ab + b) - (ab - b) = \\ ab + c - ab - b - ab + b = \\ - ab + c = c - ab$

7.

$2c - (3c + (2c - (c + 1)) + 3) = \\ 2c - (3c + (2c - c - 1) + 3 = \\ 2c - (3c + 2c - c - 1) + 3 = \\ 2c - 3c - 2c + c + 1 = - 2c + 1 = 1- 2c$