А) 3/4х=1
Х=1:3/4
Х=4/3=1 1/3
Б) 23/20у=1
У=1:23/20
У=20/23
В) 0,8а=1
а=1:0,8=10:8=1 1/4
Г) 0,7в=1
в=1:0,7=10:7=1 3/7
Д). 8/19х=8/19
х=8/19:8/19=1
Е) 12/5у=12/5
У=12/5:12/5=1
33)
cosp = (a*b)/(|a|*|b|)
a*b = 1*6 + 2*4 + 3*(-2) = 8
|a| = sqrt(1^2 + 2^2 + 3^2) = sqrt(14)
|b| = sqrt(6^2 + 4^2 + (-2)^2) = sqrt(56) = 2sqrt(14)
cosp = 8/(sqrt(14)*2sqrt(14)) = 4/14 = 2/7
p = arccos2/7
Ответ: А)
34) a(3, 4, 5), b(4, 5, -3)
cosp = (a*b)/(|a|*|b|)
a*b = 3*4 + 4*5 + 5*(-3) = 17
|a| = sqrt(3^2 + 4^2 + 5^2) = sqrt(50) = 5sqrt(2)
|b| = sqrt(4^2 + 5^2 + (-3)^2) = sqrt(50) = 5sqrt(2)
cosp = 17/(5sqrt(2)*5sqrt(2)) = 17/25*2 = 17/50
p = arccos17/50
Ответ: Б)
963-x+579=900
1542-x=900
-x=900-1542
-x=-642
x=642