2 giờ 37 phút + 3 giờ 48 phút=6 giờ 25 phút

 7 năm 3 tháng – 2 năm 9 tháng=4 năm 6 tháng 

4 giờ 32 phút x 3=816 phút nhé

16 giờ 15 phút : 5 =195 phút nhé

=195 phút hoặc 2,35 giờ nhé 

cho mình xin 1 tick nhé

\(\dfrac{15}{7}:\dfrac{7}{9}-\dfrac{4}{7}\times\dfrac{2}{9}-\dfrac{4}{7}\times\dfrac{4}{9}\)

\(=\dfrac{15}{7}\times\dfrac{9}{7}-\dfrac{4}{7}\times\dfrac{2}{9}-\dfrac{4}{7}\times\dfrac{4}{9}\)

\(=\dfrac{135}{49}-\dfrac{8}{63}-\dfrac{16}{63}\)

\(=\dfrac{1215}{441}-\dfrac{56}{441}-\dfrac{112}{441}\)

\(=\dfrac{1215-56-112}{441}\)

\(=\dfrac{1047}{441}=\dfrac{349}{147}\)

15/7 : 7/9 - 4/7 x 2/9 - 4/7 x 4/9

= 135/49 - 8/63 - 16/63

= 1159/441 - 16/63

= 1047/441 = 349/147

a) \(\dfrac{49}{81}=\dfrac{7^x}{9^x}\)(sửa đề)

\(\Leftrightarrow\left(\dfrac{7}{9}\right)^2=\left(\dfrac{7}{9}\right)^x\)\(\Rightarrow x=2\)

b) \(\dfrac{-64}{343}=\left(-\dfrac{4^x}{7^x}\right)\)(sửa đề)

\(\Leftrightarrow\left(-\dfrac{4}{7}\right)^3=\left(-\dfrac{4}{7}\right)^x\) \(\Rightarrow x=3\)

c) \(\dfrac{9}{144}=\dfrac{3^x}{12^x}\)(sửa đề)

\(\Leftrightarrow\left(\dfrac{3}{12}\right)^2=\left(\dfrac{3}{12}\right)^x\Rightarrow x=2\)

d) \(-\dfrac{1}{32}=\left(-\dfrac{1^x}{2^x}\right)\)(sửa đề)

\(\Leftrightarrow\left(-\dfrac{1}{2}\right)^5=\left(-\dfrac{1}{2}\right)^x\Rightarrow x=5\)

Mong bạn xem lại đề bài.

3 giờ 28 phút + 3 giờ 47 phút=7 giờ 15 phút
 8 năm 5 tháng – 3 năm 9 tháng=4 năm 6 tháng 
5 giờ 32 phút x 3=996 phút 
16 giờ 15 phút : 15=65 phút
9,6 ngày x 6=57,6 ngày 
18,6 giây : 3=6,2 giây
Chúc em học tốt

3 giờ 28 phút + 3 giờ 47 phút=7 giờ 15 phút
 8 năm 5 tháng – 3 năm 9 tháng=4 năm 6 tháng 
5 giờ 32 phút x 3=996 phút 
16 giờ 15 phút : 15=65 phút
9,6 ngày x 6=57,6 ngày 
18,6 giây : 3=6,2 giây

=-42x100=-4200

=-42x100=-4200

=-42x100=-4200

Câu 11:

=>4,6x=6,21

=>x=1,35

12: \(A=-\left(1.4-x\right)^2-1.4< =-1.4\)

=>x=-1,4

Câu 9:

\(\Leftrightarrow\dfrac{10a+b}{100c+90+d}=\dfrac{1}{2}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{12}+...+\dfrac{1}{92}-\dfrac{1}{97}=\dfrac{1}{2}-\dfrac{1}{97}=\dfrac{95}{194}\)

=>a=9; b=5; c=1; d=4

=>a+b+c+d=9+5+1+4=19

C

Chọn C

C

\(\dfrac{x}{9}\) < \(\dfrac{4}{7}\) < \(x\) + \(\dfrac{1}{9}\)

\(\dfrac{7x}{63}\) < \(\dfrac{36}{63}\) < \(\dfrac{63x}{63}\) + \(\dfrac{7}{63}\)

7\(x\) < 36 < 63\(x\) + 7

⇒\(\left\{{}\begin{matrix}7x< 36\\63x+7>36\end{matrix}\right.\)⇒\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\63x>36-7\end{matrix}\right.\)⇒\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\63x>29\end{matrix}\right.\)⇒\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\x>\dfrac{29}{63}\end{matrix}\right.\)

\(\dfrac{29}{63}\)<  \(x\) < \(\dfrac{36}{7}\) vì \(x\in\) Z nên \(x\in\) { 1; 2; 3; 4; 5}

⇒ \(\dfrac{x}{9}\) = \(\dfrac{1}{9}\); \(\dfrac{2}{9}\); \(\dfrac{3}{9}\); \(\dfrac{4}{9}\);\(\dfrac{5}{9}\)

\(\dfrac{x}{9}< \dfrac{4}{7}< \dfrac{x+1}{9}\)

=>\(\dfrac{7x}{63}< \dfrac{36}{63}< \dfrac{7x+7}{63}\)

\(\Rightarrow7x< 36< 7x+7\)

\(\Rightarrow x< \dfrac{36}{7}< x+1\)

\(\Rightarrow x< 5\dfrac{1}{7}< x+1\)

\(\Rightarrow x=5\)

tik cho mình nhé

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