[ (315 +372) x (3+7)] :338 + 1036

[687x 10] :1374

6870 : 1374

5

mà giải chi tiết giúp mình nha!

Ý bạn có phải là:

Tính nhanh:

\(\frac{26.13+74.14}{\left(315+372\right).3+\left(372+315\right).7}\)

đúng ko?

a) X : ( 1800 + 600 ) : 30 = 560 : ( 315 - 35 )

X:2400:30=560:280

X:80=2

X=2x80

X=160

b) 134 - 2 x 156 - 6 x 54 - 2 x  ( 9 + 6 )x X = 86

134-312-324-2x15xX=86

-502-30xX=86

-532xX=86

X=86:(-532)

X=-43/266

a. X : 2400 : 30 = 560 : 280

=> X = 2 x 2400 x 30 = 144000

b.  134 - 2 x 156 - 6 x 54 - 2 x ( 9+ 6 ) x X = 86

=> 134 - 312 - 324 - 30 x X = 86

=> 30 x X = 134 - 312 - 324 - 86 = -588

=> X = - 19,6

VD1:

a: \(5\cdot\sqrt{25a^2}-25a\)

\(=5\cdot\left|5a\right|-25a\)

=-25a-25a(a<0)

=-50a

b: \(\sqrt{49a^2}+3a\)

\(=\sqrt{\left(7a\right)^2}+3a\)

=7a+3a

=10a

c: Đặt A=\(\sqrt{64a^2}-8a\)

\(=\sqrt{\left(8a\right)^2}-8a\)

=8|a|-8a

TH1: a>=0

=>A=8a-8a=0

TH2: a<0

=>A=-8a-8a=-16a

d: Đặt \(A=\sqrt{9a^6}-3a^3\)

\(=3\cdot\sqrt{a^6}-3a^3\)

\(=3\cdot\left|a^3\right|-3a^3\)

TH1: a>=0

=>\(A=3a^3-3a^3=0\)

TH2: a<0

=>\(A=-3a^3-3a^3=-6a^3\)

VD2:

a: \(4x-\sqrt{x^2-4x+4}\)

\(=4x-\sqrt{\left(x-2\right)^2}\)

=4x-|x-2|

=4x-(x-2)(x>=2)

=4x-x+2

=3x+2

b: \(3x+\sqrt{x^2+6x+9}\)

\(=3x+\sqrt{\left(x+3\right)^2}\)

=3x+|x+3|

=3x+(-x-3)(x<-3)

=2x-3

c: \(\frac{x+6\sqrt{x}+9}{x-9}\)

\(=\frac{\left(\sqrt{x}+3\right)^2}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)}=\frac{\sqrt{x}+3}{\sqrt{x}-3}\)

d: \(\frac{\sqrt{x^2+4x+4}}{x+2}\)

\(=\frac{\sqrt{\left(x+2\right)^2}}{x+2}\)

\(=\frac{\left|x+2\right|}{x+2}=\pm1\)

\(|8-2x|=x+6\)

\(\Leftrightarrow\orbr{\begin{cases}2x-8=x+6\left(x< 0\right)\\8-2x=x+6\left(x\ge0\right)\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=14\left(loai\right)\\-3x=-2\Leftrightarrow x=\frac{2}{3}\left(nhan\right)\end{cases}}\)

vay \(x=\frac{2}{3}\)

nếu có sai bn thông cảm nha

\(\left|8-2x\right|=x+6\)

\(\Rightarrow8-2x=x+6\)

\(\Leftrightarrow\hept{\begin{cases}2x-8=x+6\left(x\le0\right)\\8-2x=x+6\left(x\ge0\right)\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}x=14\\x=\frac{2}{3}\end{cases}}\)

Mà theo đúng biểu thức, \(\left|8-2x\right|=x+6\)

\(\Rightarrow x=\frac{2}{3}\)

Vậy x = \(\frac{2}{3}\)

1 My parents go shopping twice a week

2 Hoa's house has a balcony

3 My brother usually plays badminton with his friends

4 My favorite book is Tam and Cam. What is yours?

5 There are 10 pencil cases on the table

1, My parents go shopping twice a week.

2, Hoa's house has a balcony.

3, My brother usually plays badminton with his friends.

4, My favorite book is Tam and Cam. What's yours?

5, There are ten pencil cases on the table.

Bài làm:

Ta có: \(\left(2x+3\right)\left(x+2\right)^2\left(2x+5\right)=315\)

\(\Leftrightarrow\left(2x+3\right)\left(2x+4\right)^2\left(2x+5\right)=1260\)

Đặt \(2x+4=t\)

\(Pt\Leftrightarrow\left(t-1\right)t^2\left(t+1\right)=1260\)

\(\Leftrightarrow t^4-t^2-1260=0\)

\(\Leftrightarrow\left(t^2+35\right)\left(t^2-36\right)=0\)

Mà \(t^2+35>0\Rightarrow t^2-36=0\)

\(\Leftrightarrow\orbr{\begin{cases}t=6\\t=-6\end{cases}}\Leftrightarrow\orbr{\begin{cases}2x+4=6\\2x+4=-6\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\x=-5\end{cases}}\)

\(x+x\div5\times7,5+x\div2\times9=315\)

\(x+x\times1,5+x\times4,5=315\)

\(x\times7=315\)

\(x=\frac{315}{7}=45\)

(  Mk nghĩ là dấu nhân thứ 2 của bn sửa thành dấu cộng thì đúng hơn ! )