6. Раскройте скобки и упростите: a) a - (a - (2a - 4)); в) 4y - (3y - (2y - (y + 1))); б) 7x - ((y - x) + 3y); г) 5c - (2c - ((b - c) - 2b)).

6. Раскройте скобки и упростите:

a) $$a - (a - (2a - 4)) = a - (a - 2a + 4) = a - ( - a + 4) = a + a - 4 = 2a - 4$$

Ответ: $$2a - 4$$

б) $$7x - ((y - x) + 3y) = 7x - (y - x + 3y) = 7x - (4y - x) = 7x - 4y + x = 8x - 4y$$

Ответ: $$8x - 4y$$

в) $$4y - (3y - (2y - (y + 1))) = 4y - (3y - (2y - y - 1)) = 4y - (3y - (y - 1)) = 4y - (3y - y + 1) = 4y - (2y + 1) = 4y - 2y - 1 = 2y - 1$$

Ответ: $$2y - 1$$

г) $$5c - (2c - ((b - c) - 2b)) = 5c - (2c - (b - c - 2b)) = 5c - (2c - (-b - c)) = 5c - (2c + b + c) = 5c - (3c + b) = 5c - 3c - b = 2c - b$$

Ответ: $$2c - b$$