Раскройте скобки и приведите подобные слагаемые: a) -(0,85a - 0,7b + 2,1a) + (a - 0,65b); б) 5/12 * (4,8x - 1,2y) - 3,6 * (2/9x + 7/12y). a) (-3,1a + 2,25b - a) - (1,4b - 6,3a); б) 3/8 * (2,4x - 3,2y) - 1,8 * (5/9x + 1,5y).

a) -(0.85a - 0.7b + 2.1a) + (a - 0.65b) = -0.85a + 0.7b - 2.1a + a - 0.65b = -0.85a - 2.1a + a + 0.7b - 0.65b = -1.95a + 0.05b б) 5/12 * (4.8x - 1.2y) - 3.6 * (2/9x + 7/12y) = 5/12 * 48/10x - 5/12 * 12/10y - 36/10 * 2/9x - 36/10 * 7/12y = 240/120x - 60/120y - 72/90x - 252/120y = 2x - 0.5y - 0.8x - 2.1y = 1.2x - 2.6y a) (-3.1a + 2.25b - a) - (1.4b - 6.3a) = -3.1a + 2.25b - a - 1.4b + 6.3a = -3.1a - a + 6.3a + 2.25b - 1.4b = 2.2a + 0.85b б) 3/8 * (2.4x - 3.2y) - 1.8 * (5/9x + 1.5y) = 3/8 * 24/10x - 3/8 * 32/10y - 18/10 * 5/9x - 18/10 * 15/10y = 72/80x - 96/80y - 90/90x - 270/100y = 0.9x - 1.2y - x - 2.7y = -0.1x - 3.9y