X + √(3x + 7) = 7
√(3x + 7) = 7 - x;
ОДЗ: 7 - x > 0; x < 7
(√(3x + 7))^2 =(x - 7)^2
3x + 7 = x^2 - 14x + 49
x^2 - 17x + 42 = 0
D = 289 - 4*1*42 = 121
x1 = (17 - 11)/2
x1 = 3
x2 = (17 + 11)/2
x2 = 14, не удовлетворяет ОДЗ
Ответ: х = 3
<span>³√x-9=-3
</span>³√x=-3+9
³√x=6
x=6³
x=216
Vшара = 4/3πR^3
R=∛(Vшара/(4/3π))
R=∛(99/4.186)≈2.87
1)
<span><span>-2sinxsin8x-2sinxsin2x=0
-2sinx(sin8x+sin2x)=-2sinx*2sin5xcos3x=0
sinx=0⇒x=πn
sin5x=0⇒5x=πn⇒x=πn/5
cos3x=0⇒3x=π/2+πn⇒x=π/6+πn/3
Ответ x=πn/5;x=π/6+πn/3
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2)
x-y=7
2x+y=8
прибавим
3x=15
x=5
y=5-7=-2
(5;-2)
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