đặt A=6/5.7+6/7.9+6/9.11+......+6/33.35

\(\Leftrightarrow A=3\left(\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{33\cdot35}\right)\)

\(\Rightarrow A=3\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{33}-\frac{1}{35}\right)\)

\(\Rightarrow A=3\left(\frac{1}{5}-\frac{1}{35}\right)\)

\(\Rightarrow A=3\cdot\frac{6}{35}\)

\(\Rightarrow A=\frac{18}{35}\)

Gọi A là biểu thức \(\frac{6}{5\cdot7}+\frac{6}{7\cdot9}+...+\frac{6}{33\cdot35}\)

Ta có: \(\frac{6}{5\cdot7}+\frac{6}{7\cdot9}+...+\frac{6}{33\cdot35}\)

\(\Rightarrow A=3\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{33}-\frac{1}{35}\right)\)

\(\Rightarrow A=3\left(\frac{1}{5}-\frac{1}{35}\right)=3\cdot\frac{6}{35}=\frac{18}{35}\)

Vì bạn tính A:6=28(dư 5)=>A=28.6+5=173

=>A*6=173*6=1038

Quá dễ lun !
A = 25 x 6 + 5 = 155
Giá trị của biểu thức A x 6 là : 155 x 6 = 930 

nhầm, nhầm số 28 lại viết là 25

\(\sqrt{21-6\sqrt{6}}\)

\(=\sqrt{3\left(7-2\sqrt{6}\right)}\)

\(=\sqrt{3\left(6-2\sqrt{6}+1\right)}\)

\(=\sqrt{3\left(\sqrt{6}-1\right)^2}\)

\(=\sqrt{3}\left(\sqrt{6}-1\right)\)

\(=\sqrt{3}.\sqrt{6}-\sqrt{3}.1\)

\(=9\sqrt{2}-\sqrt{3}\)

\(\sqrt{\frac{5+2\sqrt{6}}{5-2\sqrt{6}}}+\sqrt{\frac{5-2\sqrt{6}}{5+2\sqrt{6}}}=\sqrt{\frac{\left(\sqrt{2}+\sqrt{3}\right)^2}{\left(\sqrt{3}-\sqrt{2}\right)^2}}+\sqrt{\frac{\left(\sqrt{3}-\sqrt{2}\right)^2}{\left(\sqrt{3}+\sqrt{2}\right)^2}}\)

\(=\frac{\sqrt{2}+\sqrt{3}}{\sqrt{3}-\sqrt{2}}+\frac{\sqrt{3}-\sqrt{2}}{\sqrt{2}+\sqrt{3}}=\frac{\left(\sqrt{2}+\sqrt{3}\right)^2+\left(\sqrt{3}-\sqrt{2}\right)^2}{\left(\sqrt{3}-\sqrt{2}\right)\left(\sqrt{3}+\sqrt{2}\right)}=\frac{5+2\sqrt{6}+\left(5-2\sqrt{6}\right)}{3-2}=10\)

Sai de bai r ban Ngoc oi

Sai chỗ nào bạn Lâm ?

2(x^6+y^6)-3(x^4+y^4) 
= 2x^4(x² - 1) + 2y^4(y² - 1) - (x^4 + y^4) 
= - 2x^4 .y² - 2y^4 .x² - [(x² +y²)² - 2x².y²] 
= - 2x²y².(x² + y²) - 1 + 2x².y² 
= - 2x²y² - 1 + 2x²y² 
= - 1.

96:(y:6)=96:(2x12)

96:(y:6)=(2x12)

96:(y:6)=24

y:6=96:24

y:6=4

y=4x6

y=24

tick nha

\(\dfrac{9}{11}\times\left(\dfrac{6}{7}-\dfrac{5}{6}\right)\)
\(=\dfrac{9}{11}\times\left(\dfrac{36}{42}-\dfrac{35}{42}\right)\)
\(=\dfrac{9}{11}\times\dfrac{1}{42}\)
\(=\dfrac{3}{154}\)