Fill in the gaps with some, any, no, much, many, few, a few, little, a little
1. I have time to do the dishes now. The guests are coming in 15 minutes.
Let’s do the dishes together.
2. students were able to pass the exam. It was rather disappointing.
3. Can I have tea, please? It’s very cold here.
4. We need to hurry! We don't have time left.
5. Ryan had so in his mind that he couldn't concentrate on anything anymore.
6. Have you got English books at home? - Yes, I have .
7. people might like to live a lonely life, but most don't.
8. Very people are actually happy with their salaries.
9. 'Do you ever go to Atlantic City?' 'Yes, I go there times every year.'
10. This town is a very interesting place to visit. I wish I could stay here longer.
найти максимум, х∈(0, 40).
найдем производную от V=(40-X)(64-X)X=х³-104х²+2560х
она равна 3х²-208х+2560
найдем стационарные точки , приравняв производную к 0 , и решив кв. ур-ние 3х²-208х+2560=0
1) х=(104+√(104²-3·64·40))/3=(104+√((8·13)²-3·64·40)))/3=
=(104+√(8²(13²-3·40)))/3=(104+8√(13²-3·40))/3=(104+8√(169-120))/3=
=(104+8·7)/3=160/3
2) х=(104-√(104²-3·64·40))/3=(104-56)/3=16
ОСТАЛОСЬ по достаточному условию экстремума убедиться, что х=16 - точка максимума, проверяем знаки производной при переходе через эту точку, решаем неравенство 3х²-208х+2560>0, или простыми вычислениями для значений х из соответствующих промежутков.)
вот как-то так...-))
√(3х+1) = 2 - 1 - 3x
√(3х+1) = 1 - 3x
3х+1 = 1 - 6x + 9x²
9x² - 9x = 0
9x*(x - 1) = 0
9x = 0 | x-1=0
x = 0 | x = 1
Проверка: если x = 0, то √(3*0+1) + 3*0 + 1 = 2
√1 + 1 = 2
2 = 2 Подходит
Если x=1, то √(3*1+1) + 3*1 + 1 = 2
√4 + 3 + 1 = 2
6 ≠2 Не подходит
ответ: 0.
2) √(х)+x+5=11
√x = 11 - 5 -x
√x = 6-x
x = 36 - 12x + x²
x² - 13x + 36 = 0
по т. Виета: x₁ + x₂ = 13
x₁*x₂ = 36
x₁ = 4 ; x₂ = 9
Проверка, если х=4, то √4+4+5=11
11 = 11 Подходит
если х=9, то √9+9+5=11
17≠11 Не подходит
ответ: 4.
3) √(х-1) + х-1= 6
√х-1 = 6 + 1 -x
√х-1 = 7 - x
x - 1 = 49 - 14x + x²
x² - 15x + 50 = 0
x₁ + x₂ = 15
x₁ * x₂ = 50
x₁ =5, x₂ = 10
Проверка, если x=5, то √(5-1) + 5-1= 6
√4 + 4= 6
6 = 6 Подходит
если х=10, то √(10-1) + 10-1= 6
√9 + 9 = 6
12 ≠ 6 Не подходит.
ответ : 5.