tính giá trị của biểu thức:
giúp t vs, chi tiết nha
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\(2\times\frac{2}{4}\div\frac{4}{5}\)
\(\Rightarrow\frac{2}{1}\times\frac{2}{4}\div\frac{4}{5}\)
\(\Rightarrow\frac{4}{4}\div\frac{4}{5}\)
\(\Rightarrow\frac{4}{4}\times\frac{5}{4}\)
\(\Rightarrow\frac{5}{4}\)
\(\sqrt{10-2\sqrt{21}}+\sqrt{10+2\sqrt{21}}\)
\(=\sqrt{7-2\sqrt{21}+3}+\sqrt{7+2\sqrt{21}+3}\)
\(=\sqrt{\left(\sqrt{7}\right)^2-2.\sqrt{7}.\sqrt{3}+\left(\sqrt{3}\right)^2}+\sqrt{\left(\sqrt{7}\right)^2+2.\sqrt{7}.\sqrt{3}+\left(\sqrt{3}\right)^2}\)
\(=\sqrt{\left(\sqrt{7}-\sqrt{3}\right)^2}+\sqrt{\left(\sqrt{7}+\sqrt{3}\right)^2}\)
\(=\left|\sqrt{7}-\sqrt{3}\right|+\left|\sqrt{7}+\sqrt{3}\right|\)
\(=\sqrt{7}-\sqrt{3}+\sqrt{7}+\sqrt{3}\)
\(=\sqrt{7}+\sqrt{7}=2\sqrt{7}\)
Ta có: \(\sqrt{10-2\sqrt{21}}+\sqrt{10+2\sqrt{21}}\)
\(=\sqrt{7}-\sqrt{3}+\sqrt{7}+\sqrt{3}\)
\(=2\sqrt{7}\)
4/7 *1/3+5/7:2/3
\(\frac{4}{21}\)+ \(\frac{15}{14}\)= \(\frac{53}{42}\)
=(198 : 2) x 444 x 2 x 132) : 25) / 33) x 8888) : 5) x 66) : 125) x 5 =66009449.5949
a: \(\left(-35\right)+23-\left(-35\right)-47\)
\(=\left(-35\right)+23+35-47\)
\(=\left(-35+35\right)+\left(23-47\right)\)
\(=-24+0=-24\)
c: \(37-\left(-43\right)+\left(-85\right)-\left(-30\right)+15\)
\(=37+43-85+30+15\)
\(=\left(37+43\right)+30-\left(85-15\right)\)
\(=80+30-70\)
=80-40
=40
e: \(-64+\left(-111\right)+64+71\)
\(=-64-111+64+71\)
\(=\left(-64+64\right)+\left(-111+71\right)\)
=-40+0
=-40
g: \(52-\left(-15\right)+\left(+21\right)+\left(-30\right)-28-\left(+19\right)\)
\(=52+15+21-30-28-19\)
\(=\left(52+15-28-19\right)+\left(21-30\right)\)
\(=\left(67-47\right)-9\)
=20-9
=11