ta có: x¹⁰.x¹⁵     (1)

Thay x=1 vào (1) ta được:

       1¹⁰. 1¹⁵ = 1 . 1 = 1

Thay x=-1 vào (1) ta được:

       -1¹⁰. - 1¹⁵ =  -10 . -15 = -25

Thay x=4 vào (1) ta được:

        4¹⁰ .  4¹⁵ = 1048576 . 1073741824 = 11258990684

Thay x=0 vào (1) ta được:

        0¹⁰.  0¹⁵ = 0 . 0 = 0

mk cho là hs cả lớp là 1 %

Phai dat so hoc sinh la 100% chu ban

\(B\left(1-x\right)\left(3x+4\right)\)

\(\rightarrow B=\frac{1}{3}\left(3-3x\right)\left(3x+4\right)\)

\(\rightarrow B\text{⩽ }\frac{1}{3}\left(\frac{3-3x+3x+4}{2}\right)^2\)

\((BTD\)\(AM-GM)\)

\(\rightarrow B\text{⩽ }\frac{1}{3}.\frac{49}{4}\)

\(\rightarrow B\text{⩽ }\frac{49}{12}\)

Dấu '' = '' xảy ra \(\Leftrightarrow3-3x=3x+4\Leftrightarrow-\frac{1}{6}\)

Vậy \(max\)\(B=\frac{49}{12}\Leftrightarrow x=-\frac{1}{6}\)

\(B=\left(1-x\right).\left(3x+4\right)\)

Ta có :

\(B=3x+4-3x^2-4x\)

\(B=-3x^2-x+4\)

\(B=-3\left(x^2+\frac{1}{3}x-\frac{4}{3}\right)\)

\(B=-3\left(x^2+2.\frac{1}{6}.x+\frac{1}{36}-\frac{1}{36}-\frac{4}{3}\right)\)

\(B=-3\left[\left(x+\frac{1}{6}\right)^2-\frac{49}{36}\right]\)

Vì \(\left(x+\frac{1}{6}\right)^2\ge0\)

\(\Rightarrow\left(x+\frac{1}{36}\right)^2-\frac{49}{36}\ge-\frac{49}{36}\)

\(\Rightarrow B\le\frac{49}{12}\)

\(\Rightarrow\)GTLN của B là \(\frac{49}{12}\)Khi \(x=-\frac{1}{6}\)

njkuki

154

\(x-4⋮7\Rightarrow2\left(x-4\right)+7=2x-1⋮7\)

\(x-6⋮11\Rightarrow2\left(x-6\right)+11=2x-1⋮11\)

Để x nhỏ nhất

=> 2x-1 là BSC nhỏ nhất của 7 và 11 => 2x-1=77=> x=39

x mod 7 =4 => x-4 mod 7 =0 => x-4 + 42=( x+38) mod 7 =0

x mod 11 =6 => x-6 mod 11 =0=> x-6 +44= (x+38) mod 11 =0

Vậy (x+38) chia hết cho 7 và 11

(x+38) là BSCNN của (7,11)=77

Vậy số cần tìm là x= 77-38= 39

Đáp số x=39

số đó là 22

Gọi số tự nhiên đó là a :

a - 2 chia hết cho 8

a - 2  chia hết cho 9

a - 2  chia hết cho 12

a thuộc N*; a thuộc BCNN(8,9,2)

Ta có : 

8 = 2³

9 = 3²

12 = 2² . 3

BCNN(8,9,12) = 2³ . 3 ²=  72

=> a - 2 tthuộc {72}

=> a thuộc {70}

Vậy số tự nhiên nhỏ nhất khi chia cho 8, 9 và 12 được số dư lần lượt là 6,7 và 10 là : 70

Semester at school is coming to an end. Here comes our summer vacation.

I'm going to go to the countryside to enjoy the vacation with my family. My grandparents live there. They will tell me numerous intersting stories. I miss them much.

Along the dikes on big paddy fields, I will fly kites with my brother and the children there. We will also go fishing together. There will be lots of fresh fruits and I will have a chance to enjoy them all. 

My summer vacation will certainly be great. I will have much leisure to relax and play.

I have itchy feet, so I always have a detailed plan for the next holiday trip in mind.

This time, I am going to wait for my children’s summer vacation so that I can take the whole family on a trip together. I am a family person and I love to travel with my loved ones. And, you know, summer won’t be complete without sun tan and beach snapshots. Therefore, my destination must be a seaside city and Vinh Hy Bay is my ideal place. I have heard about this place a long time ago, a friend of mine highly recommended this place after her trip there. It is known for its natural scenic beauty and delicious fresh seafood at an affordable price.

I was curious, but couldn’t find time to travel there due to my tight working schedule. But this summer we are going to make it. It’s only a 4-hour ride from our city to the bay, so I am going to go by bike as if I were going backpacking. One reason luring us to this place is that it’s a pristine island, which means it won’t be crowded with tourists and the food here won’t be overpriced. Un other beaches which offer a variety of water sports canoeing, scuba-diving, water-skiing, and skydiving, there will not be many activities to do in Vinh Hy bay apart from sun-bathing and eating seafood. But this is going to be family time, and to me, spending time together is already enough.

In case my children get bored, so I am going to bring some family games UNO and castle-building tools to enjoy time on the beach together. I am in dire need of this vacation as I want to escape from a stressful workload and pressure from city life for a while with my kids and my spouse. Also, I think it is a good idea to reward my children with a trip after studying hard throughout the school year