49/7= 7 - 1 часть
7*4=28 - 4 части
Х² - 2х - 3 = 0
D = 2² + 4 * 1 * 3 = 4 + 12 = 16
х₁ = 2 + 4 / 2 * 1 = 3
х₂ = 2 - 4 / 2 * 1 = -2 / 2 = -1
-5m(-4n)8k=(-5)(-4).8mnk=160mnk
koefficient: 160
2:4/5=2*5/4=2,5часа
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15c+45-12=78
15c+33=78
15c=78-33
15c=45
c=45÷15
c=3
(6y+14)÷2+15=40
3y+7+15=40
3y=40-7-15
3y=18
y=18÷3
y=6