2·(y+7)-3·y=5·y-3·(4-2·y)
2·y+14-3·y=5·y-12+6·y
14+12=11·y-2·y+3·y
12·y=26
y=26/12=13/6=2 1/6
Проверка:
2·(13/6+7)-3·13/6=5·13/6-3·(4-2·13/6)
2·13/6+14-13/2=65/6-12+3·13/3
13/3+14-13/2=65/6-12+13
(26+84-39)/6=65/6+1
(110-39)/6=(65+6)/6
71/6=71/6 верно
2,5·(x+4)-0,5=1,2·(5·x-3)-2,4
2,5·x+10-0,5=6·x-3,6-2,4
9,5+3,6+2,4=6·x-2,5·x
3,5·x=15,5
x=15,5/3,5=155/35=31/7=4 3/7
Проверка:
2,5·(31/7+4)-0,5=1,2·(5·31/7-3)-2,4
2,5·(31+28)/7-0,5=1,2·155/7-3,6-2,4
2,5·59/7-0,5=186/7-6
147,5/7-0,5=(186-42)/7
(147,5-3,5)/7=144/7
144/7=144/7 верно
2·(y+7)-3·y=5·y-3·(4-2·y)
2·y+14-3·y=5·y-12+6·y
14+12=11·y-2·y+3·y
12·y=26
y=26/12=13/6=2 1/6
Проверка:
2·(13/6+7)-3·13/6=5·13/6-3·(4-2·13/6)
2·13/6+14-13/2=65/6-12+3·13/3
13/3+14-13/2=65/6-12+13
(26+84-39)/6=65/6+1
(110-39)/6=(65+6)/6
71/6=71/6 верно
2,5·(x+4)-0,5=1,2·(5·x-3)-2,4
2,5·x+10-0,5=6·x-3,6-2,4
9,5+3,6+2,4=6·x-2,5·x
3,5·x=15,5
x=15,5/3,5=155/35=31/7=4 3/7
Проверка:
2,5·(31/7+4)-0,5=1,2·(5·31/7-3)-2,4
2,5·(31+28)/7-0,5=1,2·155/7-3,6-2,4
2,5·59/7-0,5=186/7-6
147,5/7-0,5=(186-42)/7
(147,5-3,5)/7=144/7
144/7=144/7 верно
2) -1 3/11*(-2 2/21) = -14/11*(-44/21) = (2*7)/11*(4*11)/(3*7) = 8/3 = 2 2/3
3) -2,72:(-0,4) = 2,72:(0,4) = 27,2/4 = (24+3,2)/4 = 6+0,8 = 6,8
4) 15,45:(-15) = -(15+15*0,03)/15 = -1,03
2. 1)-1,5a*(-6b) = 3/2*a*6*b = 3*3*a*b = 9ab
2) -4m - 15n + 3m + 18n = -4m + 3m - 15n + 18n = -m + 3n = 3n - m
3) b + (7-b) - (14-b) = b + 7 - b - 14 + b = -7 + b = b - 7
4) -2(x-3) + 4(x+1) = -2x + 6 + 4x + 4 = 2x + 10