-42x-35>-5-3x
-42x+3x>-5+35
-39x>30
x< - 30/39
А) 2x - y = 7
x = 3 + y
- 2x = - 6 - 2y
2x = y + 7
0 = - y + 1
y = 1
x = 3 + 1 = 4
Ответ ( 4 ; 1 )
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б) x = 2y + 1
2x + 4y = 18
2x = 18 - 4y
- 2x = - 4y - 2
0 = 18 - 2 - 4y - 4y
16 - 8y = 0
y = 2
x = 4 + 1 = 5
Ответ ( 5 ; 2 )
B1=18
q=2/3
S=b1/(1-q)=18:(1-2/3)=18:1/3=18*3=54