Tìm GTLN của A= \(\dfrac{\sqrt{x-9}}{5x}\)

Bài 5: Cho a,b>0. Chứng minh

\(\sqrt{a^2-b^2}+\sqrt{2ab-b^2}\ge a\)

Bài 6: Cho a,b,c>0. Chứng minh:

\(\dfrac{a}{b+c}+\dfrac{b}{a+c}+\dfrac{c}{a+b}\ge\dfrac{3}{2}\)

Đây là bất đẳng thức nesibit cho 3 số thực dương. mình có xem qua trên mạng rồi nhưng không hiểu cho lắm. Mong các bạn giúp đỡ, cảm ơn các bạn nhiều!!! 사랑해요. 암사힙니다

Do a chia cho 5 dư 3=> a=5k+3 (k \(\in N\))

b chia cho 5 dư 4=> b= 5q+4 ( \(q\in N\))

=> ab= (5k+3)(5q+4)

ab= 25kq+20k+15q+12

ab= 25kq+20k+15q+10+2

ab= 5(5kq+4k+3q+2)+2

vì 5 \(⋮\) 5

=> 5(5kq+4k+3q+2) \(⋮\) 5

=> 5(5kq+4k+3q+2) +2 chia cho 5 dư 2

Vậy ab chia cho 5 dư 2 (đpcm)

----An cố gắng học tốt Toán nhá----

Ta có :

7⁴ⁿ-1=(7⁴)ⁿ - 1=(.....1)ⁿ - 1=.....1 - 1=.....0 => chia hết cho 5

(x-5)(2x+3)-2x(x-3)+x+7

= 2x²+3x-10x-15-2x²+6x+x+7

= (2x²-2x²)+(6x+x+3x-10x)-(15-7)

= 0+0-8

= -8

vậy giá trị của biểu thức (x-5)(2x+3)-2x(x-3)+x+7 không phụ thuộc vào giá trị của biến

1, Nam like hot weather because he can go swimming

2,Who is your favorite sportman?- Ronaldo

3,What did you do last Sunday?

4, "Tom and Jerry"cartoons are made in USA

5, Many women do aerobics to keep fit

6, Don't talk in class, please! Listen to the teacher

7 ,Red river is the longest river in VN

8,My father loves watching news on TV

9, My house is the farthest from school because no one lives far from to school than I

10, Playing soccer and watching TV are the most common activities after school in VN

11, How long have you lived here?=> For 2 years

12, Tea is the most popular drink in Britain

13, Cool weather is very cool we go fishing

14 Skating is often played when it's snowy

--Câu 13 cấu trúc hơi lạ, bạn xem lại nhé--

- This morning i met my old teacher. I hadn't seen her for ages

-> This morning i met my old teacher who I hadn't seen for ages.

- The picture has been stolen. You were talking about it

->The picture has been stolen which you were talking about.