\(4^{15}\cdot9^{15}\le2^x\cdot3^x\le18^{16}\cdot2^{16}\)

\(\Rightarrow\left(2^2\right)^{15}\cdot\left(3^2\right)^{15}\le2^x\cdot3^x\le\left(2\cdot3^2\right)^{16}\cdot2^{16}\)

\(\Rightarrow2^{30}\cdot3^{30}\le2^x\cdot3^x\le2^{32}\cdot3^{32}\)

\(\Rightarrow x=31\)

a)Đặt  \(A=11-10x-x^2=-\left(x^2+10x+25\right)+36=-\left(x+5\right)^2+36\le36\)

Dấu = xảy ra \(\Leftrightarrow x+5=0\Leftrightarrow x=-5\)

Vậy GTLN của A là 36 \(\Leftrightarrow x=-5\)

giải

54 phút =9/10 giờ;40 phút= 2/3 giờ

Vận tốc ô tô đi lên dốc là:

15,3:9/10=17(km/h)

Vận tốc ô tô đi xuống dốc là:

24:2/3=36(km/h)

Vận tốc trung bình cộng của ô tô khi lên dóc và xuống dốc là:

(36+17):2=26,5(km/h)

Đáp số: 26,5 km/h

1.What would you like for dinner? 

I'd like some rice and chicken  for dinner 

2.How much is a cake?

A cake is 5,000 đ

3.How do you feel?  

I feel tired

4.How often do you go fishing? 

I go fishing once a week

5. Are you often play badminton in the fall?

Yes. I often play badminton in the fall

6. What is the weather like in spring?

It's warm in the spring.

7. What are they doing at the moment?

They are playing table tennis  at the moment

8.What do you play?

I play soccer

9. What does she do in her free time?

She does aerobics in her free time

10. How many rice does he want?

He wants a kilo of rice

câu 1 : -1 / 15

câu 2 :  11

câu 3 : -143/10

câu 4 : -21 / 5

câu 5 : 60

It's good for children to revise their lessons before tests

Ta có:

3⁰+3²+...+3²⁰⁰²

=1+3²+3³+...+3²⁰⁰²

Coi A=1+3²+3³+...+3²⁰⁰²

=>3A=3+32+...+3²⁰⁰³

=> 2A=3A-A=(3+3³+...+3²⁰⁰³)-(1+3²+...+3²⁰⁰²)

                  =3+3²⁰⁰²-1-3²

                  =3²⁰⁰²+3-1-9

                  =3²⁰⁰²-7

=> A=\(\frac{3^{2002}-7}{2}\)

a) Ta có : MN//PQ//OE nên ta có góc MOE = góc NMO = 45 độ (2 góc so le trong)

mặt khác ta có góc QPO + góc EOP = 180 độ ( 2 góc trong cùng phía bù nhau)

suy ra góc EOP = 180 độ - góc QPO = 180 độ - 130 độ = 50 độ

Mà góc MOP = góc MOE + góc EOP = 45 độ + 50 độ = 95 độ 

Once a poor farmer had a daughter named Little Pea. After his wife died the farmer married again. his new wife had a daughter. Stout Nut. Unfortunately, the new wife was very curel to Little Pea. Little Pea had to do chores all day. This made Little Pea's father very upset. he soon died of a broken heart.
Summer came and went. In the fall, the village held its harvest festival. That year, every one was excited as the prince wanted to choose his wife from the village. Stout Nut's mother made new clothes for hẻ, but poor Little Pea had none.
However, before the festival started, a fairy appeared and magically changed Little Pea's rags into beautiful clothes.
As Little Pea ran to the festival, the dropped one of hẻ shoes and lost it. when the prince found the shoe, he decided to marry the girl who owned it. Of course the shoe fiied Little Pea, and the prince immediately fell in love with her.

Chiều dài hình chữ nhật là :

160 : 2 - 30 = 50 (m)

Diện tích hình chữ nhật là :

50 x 30 = 1500 (m²)

Số kg rau người ta thu được trên thửa ruộng đó là :

1500 : 10 x 15 = 225 (kg)

ĐS : 225kg

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