Предмет: Алгебра, автор: daryashepina

решить систему :
360/y - 360/x = 2
360/y+30 - 360/x+30 = 1

Ответы

Автор ответа: Матов

0

$frac{360}{y}-frac{360}{x}=2\ frac{360}{y+30}-frac{360}{x+30}=1\\ frac{360x-360y}{xy}=2\ frac{360(x+30)- 360(y+30)}{(y+30)(x+30)}=1\ \ frac{360x-360y}{yx+30y+30x+900}=1\ frac{360x-360y}{xy}=2\\ \ 360x-360y=yx+30(y+x)+900\ 360x -360y=2yx\ \ yx+30(y+x)+900=2yx\ 30(y+x)+900=yx 30y+30x+900=yx\ 30y-yx=-30x-900\ y(30-x)=-30x-900\ y=frac{-30x-900}{30-x}\ y=frac{-30x-900}{30-x}\ frac{360(30-x)}{-30x-900}-frac{360}{x}=2\ x^2-78x-1080=0\ D=sqrt{10404}\ x_{1}=90\ x_{2}=-12\$
$y_{1}=-12frac{6}{7}\ y_{2}=60$

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2. What … your friend? He … a teacher.
A) Am/are
B) are /is
C) Is/is
D) to be/is
E) Are /am
3. It (to be) difficult for her.
A) were
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4. My friend ( to spend ) his week-end in the country before he entered the University.
A) had spent
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5. I don’t know her … address.
A) cousins
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C) cousins’
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E) cousin’
6. … supper is … last meal of … day.
A) the, -, -,
B) a, a, -,
C) the, -, -,
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C) most young
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A) His
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A) much
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E) a few
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A) by
B) with
C) –
D) to
E) at
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A) be
B) been
C) am
D) is
E) are
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A) Bob knows?
B) Do Bob knows?
C) Does Bob know?
D) Is Bob knows?
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A) come
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D) will come
E) coming
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C) will / be finish
D) shall / be finish
E) will be / finish

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A) am
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C) do
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