xin lỗi mk viết nhầm, là 625\(^2\)nhé

Bài 1 : Rút gọn các phân số sau đến tối giản :

a) \(\dfrac{3.21}{14.15}=\dfrac{3.3.7}{2.7.3.5}=\dfrac{1.3.1}{2.1.1.5}=\dfrac{3}{10}\)

b) \(\dfrac{49+49.7}{49}=\dfrac{49\left(1+7\right)}{49}=\dfrac{49.8}{49}=\dfrac{1.8}{1}=\dfrac{8}{1}=8\)

h

ko biết

a. 60%x + 0,4x + x : 3 = 2

0.6x + 0,4x + x : 3 = 2

x(0,6 + 0,4 : 3 ) = 2

\(x.\frac{1}{3}=2=>x=2:\frac{1}{3}=\frac{1}{6}\)

câu B tự làm nha .

Câu hỏi của Lê Thị Minh Trang - Toán lớp 6 - Học toán với OnlineMath

Xem bài 1 nhé !

Bài 1:

Xét vế phải :

\(P=\frac{99}{50}-\frac{97}{49}+...+\frac{7}{4}-\frac{5}{3}+\frac{3}{2}\)\(-1=2\)\(\left(\frac{99}{100}-\frac{97}{98}+...+\frac{7}{8}-\frac{5}{6}+\frac{3}{4}-\frac{1}{2}\right)\)

\(=2\left(\left(1-\frac{1}{100}\right)-\left(1-\frac{1}{98}\right)+...+\left(1-\frac{1}{4}\right)-\left(1-\frac{1}{2}\right)\right)\)

\(=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{98}-\frac{1}{100}\right)\)

\(=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)

\(=\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}\right)-2\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+...+\frac{1}{50}\right)\)

\(=\left(1+\frac{1}{2}+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{25}+\frac{1}{26}+...+\frac{1}{50}\right)-\left(1+\frac{1}{2}+...+\frac{1}{25}\right)\)

\(=\frac{1}{26}+\frac{1}{27}+...+\frac{1}{49}+\frac{1}{50}\)

Đẳng thức được chứng tỏ là đúng

Bài 2 :

Đặt \(A'=\frac{3}{4}.\frac{4}{5}.\frac{7}{8}...\frac{4999}{5000}\)

Rõ ràng \(A< A'\)

SUY RA \(A^2< AA'=\frac{2}{50000}=\frac{1}{2500}=\left(\frac{1}{50}\right)^2\)

Nên \(A< \frac{1}{50}=0,02\)

Chúc bạn học tốt ( -_- )

1) \(x:\dfrac{2}{3}=150\)

\(\Leftrightarrow x=150.\dfrac{2}{3}\)

\(\Leftrightarrow x=100\).

2) \(\dfrac{35}{9}:x=\dfrac{35}{6}\)

\(\Leftrightarrow x=\dfrac{35}{9}:\dfrac{35}{6}\)

\(\Leftrightarrow x=\dfrac{2}{3}\).

3) \(\dfrac{49}{7}:x=\dfrac{49}{5}\)

\(\Leftrightarrow x=\dfrac{49}{7}:\dfrac{49}{5}\)

\(\Leftrightarrow x=\dfrac{5}{7}\).

4) \(1-\left\{5\dfrac{4}{9}+x-7\dfrac{7}{18}\right\}:15\dfrac{3}{5}=0\)

\(\Leftrightarrow1-\left\{\dfrac{49}{9}+x-\dfrac{133}{18}\right\}:\dfrac{78}{5}=0\)

\(\Leftrightarrow\left\{\dfrac{-35}{18}+x\right\}:\dfrac{78}{5}=1-0\)

\(\Rightarrow\dfrac{-35}{18}+x=1.\dfrac{78}{5}\)

\(\Leftrightarrow\dfrac{-35}{18}+x=\dfrac{78}{5}\)

\(\Rightarrow x=\dfrac{1579}{90}\).

Gọi a,b,c.. cho dễ nhé.Thớt vui tính quá, dấu phẩy cũng không viết hộ con dân =)))

a, \(x:\dfrac{2}{3}=150\)

\(\Leftrightarrow x=150.\dfrac{2}{3}\)

\(\Leftrightarrow x=100\)

Vậy...

b, \(\dfrac{35}{9}:x=\dfrac{35}{6}\)

\(\Leftrightarrow x=\dfrac{35}{9}:\dfrac{35}{6}\)

\(\Leftrightarrow x=\dfrac{2}{3}\)

Vậy...

c, \(\dfrac{49}{7}:x=\dfrac{49}{5}\)

\(\Leftrightarrow x=\dfrac{49}{7}:\dfrac{49}{5}\)

\(\Leftrightarrow x=\dfrac{5}{7}\) Vậy...

d, \(1-\left\{5\dfrac{4}{9}+x-7\dfrac{7}{18}\right\}:15\dfrac{3}{4}=0\)

\(\Leftrightarrow1-\left\{\dfrac{49}{9}+x-\dfrac{133}{18}\right\}:\dfrac{63}{4}=0\)

\(\Leftrightarrow1-\left\{x-\dfrac{35}{18}\right\}:\dfrac{63}{4}=0\)

\(\Leftrightarrow1-\left(\dfrac{\left(18x-35\right).4}{18.63}\right)=0\)

\(\Leftrightarrow1-\left(\dfrac{72x-140}{1134}\right)=0\)

\(\Leftrightarrow1-\dfrac{72x-140}{1134}=0\)

\(\Leftrightarrow\dfrac{1134-72x+140}{1134}=0\)

\(\Leftrightarrow1274-72x=0\)

\(\Leftrightarrow72x=1274\)

\(\Leftrightarrow x=\dfrac{637}{36}\)

Vậy...

Xét vế phải :

\(VP=\frac{99}{50}-\frac{97}{49}+...+\frac{7}{4}-\frac{5}{3}+\frac{3}{2}-1\)

\(=2.\left(\frac{99}{100}-\frac{97}{98}+...+\frac{7}{8}-\frac{5}{6}+\frac{3}{4}-\frac{1}{2}\right)\)

\(=2\left[\left(1-\frac{1}{100}\right)-\left(1-\frac{1}{98}\right)+...+\left(1-\frac{1}{4}\right)-\left(1-\frac{1}{2}\right)\right]\)

\(=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{98}-\frac{1}{100}\right)\)

\(=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)

\(=\left(1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{49}+\frac{1}{50}\right)-2\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+...+\frac{1}{50}\right)\)

\(=\left(1+\frac{1}{2}+\frac{1}{2}+\frac{1}{4}+...+\frac{1}{25}+\frac{1}{26}+...+\frac{1}{50}\right)-\left(1+\frac{1}{2}+...+\frac{1}{25}\right)\)

\(=\frac{1}{26}+\frac{1}{27}+...+\frac{1}{49}+\frac{1}{50}=VT\Rightarrow\left(đpcm\right)\)

trả lời:

\(a.=\frac{17}{72}\)

hk tốt

trả lời:

\(b.=-16\)

hk tốt

\(\frac{5-\frac{5}{7}-\frac{5}{49}}{4-\frac{4}{7}-\frac{4}{49}}+\frac{1,5+75\%-\frac{3}{8}}{0.625-\frac{5}{2}-125\%}\)

\(=\frac{5.\left(\frac{1}{5}-\frac{1}{7}-\frac{1}{49}\right)}{4\cdot\left(\frac{1}{4}-\frac{1}{7}-\frac{1}{49}\right)}+\frac{\frac{3}{2}+\frac{3}{4}-\frac{3}{8}}{\frac{5}{8}-\frac{5}{2}-\frac{5}{4}}\)

\(=\frac{5}{4}+\frac{3\cdot\left(\frac{1}{2}+\frac{1}{4}-\frac{1}{8}\right)}{5\cdot\left(\frac{1}{8}-\frac{1}{2}-\frac{1}{4}\right)}\)

\(=\frac{5}{4}+\left(-\frac{3}{5}\right)\)

\(=\frac{13}{20}\)

kết quả là 109/116