1. A

2. B

3. A

4. B

1.    444 x 5 = 222 x 2 x 5 = 222 x 10 = 2220
2.    282 x 5 = 280 + 2 x 5 = 280 x 10 = 2800
3.    4 x 8 x 7 x 25 = (8 x 7) x (25 x4) = 56 x 100 = 5600
4.    25 x 8 x 9 = (25 x 4) x (4 x 9) = 100 x 36 = 3600
a.Đúng         b.Sai

1. sai

2. Sai

3. đúng

4.sai

13 x 3 - 2 = 13 : S

180 + 30 : 6 = 35 : S

30 + 60 x 2 = 180 : S

282 - 100 : 2 = 232 : Đ

37 - 5 x 5 = 12 : Đ

180 : 6 + 30 = 60 : Đ

30 + 60 x 2 = 150 : Đ

282 - 100 : 2 = 91 : S

\(x\times282-270\times x=1512\\ x\times\left(282-270\right)=1512\\ x\times12=1512\\ x=1512:12\\ x=126\)

x = 126

x×282−270×x=1512

x×(282−270)=1512

x×12=1512

x=1512:12

x=126

câu 1= 13288

câu 2= 14368

câu 1= 13288

câu 2=14368

chúc bạn học giỏi

1C

2A

1C        2A

x x 45 =282 +123=405

x = 405/45 =9 k nha

(x * 45) -123 = 282 

45x = 405

x= 9

( X x 45 ) - 123 = 282

X x 45 = 282 -123

X x 45 = 405 

X        = 405 : 45

X        = 9

a)   X : 8 = 101

       X = 101 x 8

       X = 808

b)   X : 5 = 117

       X = 117 x 5

       X = 585

c)   X : 3 = 282

       X = 282 x 3

       X = 846

\(\Leftrightarrow36\left(x+6\right)+36\left(x-6\right)=\dfrac{9}{2}\left(x^2-36\right)\)

\(\Leftrightarrow x^2\cdot\dfrac{9}{2}-162-72x=0\)

\(\Leftrightarrow9x^2-144x-324=0\)

\(\Leftrightarrow x^2-16x-36=0\)

=>(x-18)(x+2)=0

=>x=18 hoặc x=-2

ĐKXĐ:\(x\ne\pm6\)

\(\dfrac{36}{x-6}+\dfrac{36}{x+6}=4,5\\ \Leftrightarrow36\left(\dfrac{1}{x-6}+\dfrac{1}{x+6}\right)=4,5\\ \Leftrightarrow\dfrac{x+6}{\left(x-6\right)\left(x+6\right)}+\dfrac{x-6}{\left(x-6\right)\left(x+6\right)}=\dfrac{1}{8}\\ \Leftrightarrow\dfrac{x+6+x-6}{x^2-36}=\dfrac{1}{8}\\ \Leftrightarrow\dfrac{2x}{x^2-36}=\dfrac{1}{8}\\ \Leftrightarrow x^2-36=16x\\ \Leftrightarrow x^2-16x-36=0\\ \Leftrightarrow\left(x^2+2x\right)-\left(18x+36\right)=0\\ \Leftrightarrow x\left(x+2\right)-18\left(x+2\right)=0\\ \Leftrightarrow\left(x+2\right)\left(x-18\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-2\left(tm\right)\\x=18\left(tm\right)\end{matrix}\right.\)