Решите систему уравнений подстановки 60 а)a+5b=7 3a-2b=4 б)u-3v=17 u-2v=-13 в)p+12q=11 5p-3q=3 г)y-2x=4 7x-y=1 д)2m=n+0,5 3m-5n=12 е)25-x=-4y 3x-2y=30

1) a = 7 - 5b
3(7 - 5b) -2b = 4

a = 7 - 5b
-17b = -17

b = 1
a = 7 - 5 = 2

(2; 1)

2) u = 17 + 3v
17 + 3v - 2v = -13

u = 17 + 3v
v = -30

u = 17 - 90 = -73

(-73; -30)

3) p = 11 - 12q
5(11 - 12q)  - 3q = 3

p = 11 - 12q
-63q = -52

q = 52/63
p = 11 - 208/21 = 23/21

(23/21; 52/63)

4) y= 4 + 2x
7x - 4 - 2x = 1

y = 4 + 2x
5x = 5

x = 1
y = 4 + 2 = 6

(1; 6)

5) n = 2m - 0,5
3m - 5(2m - 0,5) = 12

n = 2m - 0,5
-7m = 9,5

m = 19/14
n = 19/7 - 1/2 = 31/14

(19/14; 31/14)

6) x = 25 + 4y
3(25 + 4y) - 2y = 30

x = 25 + 4y
10y = -45

y = -4,5
x = 25 - 18 = 7

(7; -4,5)