Предмет: Алгебра, автор: bonton

Помогите, вроде правильно составляю уравнения, но решить их не могу! Посмотрите, пожалуйста!!!

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Ответы

Автор ответа: nafanya2014

Все решается.
Ответы приближенные.
1) -4,9t²+32t+1,6=0
   49t²-320t-16=0
D=(-320)²-4·49·(-16)=102400+3136=105536≈(324,86)²
t≈(320+324,86)/98=6,5
второй корень не считаем, он отрицательный.

2)-4,9t²+32t+1,6=20
   49t²-320t+184=0
D=(-320)²-4·49·184=102400-36064=66336≈(257,56)²
t₁ ≈ (320-257,56)/98=0,6 или   t₂ ≈ (320+257,56)/98=5,89

3)-4,9t²+30t=40
   49t²-300t+400=0
D=(-300)²-4·49·400=90000-78400=11600≈(107,7)²
t ≈ (320-107,7)/98=2,17 или   t ≈ (320+107,7)/98=4,36

Автор ответа: bonton

спасибо огромное!!!!!!!!!!!

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Read the text and answer the questions(do not forget full stops!):

It's 7:30 pm at Lisa's house and she's in her room doing her homework. However, homework is just one of the things she's doing while her eyes are fixed on the computer screen. As well as studying for her Biology exam, Lisa is also listening to music, chatting with her best friend online, downloading songs and occasionally texting people on her mobile phone. "My parents keep telling me off for multi-tasking while studying, but they don't understand that it helps me concentrate," she says.
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What things is Lisa doing while she is doing her homework?

What does multi-tasking help Lisa in?

How much time a day do young people spend using different types of media?

When does multi-tasking have a bad impact ?

What is the result of dividing the attention between too many activities?

What do the students do at the sound of the bell?

What has become extensions of young people nowadays?

What can be neither denied or replaced?