= -1 nha

4,05 bạn nhé

\(A=\frac{50x48x8}{6x1x100}x\frac{1}{2}x\frac{1}{3}x\frac{3}{4}x...x\frac{18}{19}x\frac{19}{20}\)

\(A=\frac{4}{1}x\frac{1}{1}x\frac{1}{20}\)

\(A=\frac{4}{20}=\frac{1}{5}\)

K tui nhó

Trả lời:

1) \(\left(\sqrt{x}+1\right)\left(\sqrt{x}-2\right)=\left(\sqrt{x}\right)^2-2\sqrt{x}+\sqrt{x}-2=x-\sqrt{x}-2\)

2) \(\left(x+4\right)\left(x-2\right)-\left(x-3\right)^2=x^2-2x+4x-8-\left(x^2-6x+9\right)\)\(=x^2+2x-8-x^2+6x-9=8x-17\)

3)  \(3x\left(2x^3-3x^2+5\right)=6x^4-9x^3+15x\)

135/42

Tìm x, y

Áp dụng tính chất dãy tỉ số bằng nhau:

\(\frac{x-y}{3}=\frac{x+y}{13}=\frac{x-y+x+y}{3+13}=\frac{2x}{16}=8\)

Vì \(\frac{x-y}{3}=\frac{x+y}{13}=\frac{xy}{200}\) nên \(\frac{xy}{200}=\frac{x}{8}=\frac{25x}{200}\)

\(\Rightarrow xy=25x\)

\(\Rightarrow y=25\)

\(\Rightarrow\frac{x-25}{3}=\frac{x+25}{13}\)

\(\Rightarrow13\left(x-25\right)=3\left(x+25\right)\)

\(\Rightarrow13x-325=3x+75\)

\(\Rightarrow10x=400\Rightarrow x=40\)

Vậy x = 40 và y = 25

850:100.23.4=198.9

= 198,9

k đúng nha 

ai cần điểm hỏi đáp mình k cho

\(A=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...+\frac{1}{1+2+3+4+...+2021}\)

\(A=\frac{1}{\frac{2\times3}{2}}+\frac{1}{\frac{3\times4}{2}}+\frac{1}{\frac{4\times5}{2}}+...+\frac{1}{\frac{2021\times2022}{2}}\)

\(A=2\times\left(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+...+\frac{1}{2021\times2022}\right)\)

\(A=2\times\left(\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+\frac{5-4}{4\times5}+...+\frac{2022-2021}{2021\times2022}\right)\)

\(A=2\times\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{2021}-\frac{1}{2022}\right)\)

\(A=2\times\left(\frac{1}{2}-\frac{1}{2022}\right)\)

\(A=\frac{1010}{1011}\)

6061 bạn nhé