2x-3y=3
2x/3+y=1/3 |*3
2x-3y=3
2x+3y=1
2x-3y=3
+
2x+3y=1
4x=4
x=1
2x+3y=1
2*1+3y=1
3y=-1
y=-1/3
x=2
y=1/3
- X - Y - Z = - 4
X + Y - Z = 2
- 2Z = - 2
Z = 1
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X + Y = 4 - 1
X + Y = 3
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2X - Y = 1 - 1
2X - Y = 0
----------------
X + Y = 3
Y = 3 - X
2X - ( 3 - X) = 0
2X - 3 + X = 0
3X = 3
X = 1
------------------
1 + Y = 3
Y = 3 - 1
Y = 2
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Ответ X = 1; Y = 2 ; Z = 1
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Проверка
1) 1 + 2 + 1 = 4 ; 4 = 4
2) 1 + 2 - 1 = 2 ; 2 = 2
3) 2 - 2 + 1 = 1 ; 1 = 1
Все решается по формуле суммы n членов геометрической прогрессии.
1) у= tgx³
y' = 3x²/cos²x³
2) y=2arctg3/x
y' = -2*(3/x²)/(1+(3/x)²) = -6/(x²(1+(3/x)²)
3) y=2arcctg lnx/x
y' = 2*(1/x)*(-1/x²)/(1/(lnx/x)) = -2/(x³*lnx/x)