\(\begin{array}{l}a)\sqrt {0,49}  + \sqrt {0,64}  = 0,7 + 0,8 = 1,5;\\b)\sqrt {0,36}  - \sqrt {0,81}  = 0,6 - 0,9 =  - 0,3;\\c)8.\sqrt 9  - \sqrt {64}  = 8.3 - 8 = 24 - 8 = 16;\\d)0,1.\sqrt {400}  + 0,2.\sqrt {1600}  = 0,1.20 + 0,2.40 = 2 + 8 = 10\end{array}\)

Bai 1

a) \(\sqrt{0,36}+\sqrt{0,49}=0,6+0,7=1,3\)

b) \(\sqrt{\frac{4}{9}}-\sqrt{\frac{25}{36}}=\frac{2}{3}-\frac{5}{6}\)

=\(-\frac{1}{6}\)

Bài 2

a)\(x^2=81\Rightarrow\left[{}\begin{matrix}x=9\\x=-9\end{matrix}\right.\)

b) \(\left(x-1\right)^2=\frac{9}{16}\)

\(\Rightarrow\left[{}\begin{matrix}x-1=\frac{3}{4}\\x-1=\frac{-3}{4}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\frac{7}{4}\\x=\frac{1}{4}\end{matrix}\right.\)

c) \(x-2\sqrt{x}=0\Rightarrow\sqrt{x}\left(\sqrt{x}-2\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

d) \(x=\sqrt{x}\Rightarrow x-\sqrt{x}=0\Rightarrow\sqrt{x}\left(\sqrt{x}-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)

= 9/4 - (1/2- 3/2)^2 :4/5

= 9/4 - 1 : 4/5

= 9/4 - 5/4

= 1

a)\(\sqrt{0,36}\)+\(\sqrt{0,49}\)=0,6+0,7=1,3

b)\(\sqrt{\frac{4}{9}}\)-\(\sqrt{\frac{25}{36}}\)=2/3-5/6=4/6-5/6=-1/6

a) \(\sqrt{0,36}+\sqrt{0,49}=\sqrt{\left(0,6\right)^2}+\sqrt{\left(0,7\right)^2}=0,6+0,7=1,3\)

b) \(\sqrt{\frac{4}{9}}-\sqrt{\frac{25}{36}}=\sqrt{\left(\frac{2}{3}\right)^2}-\sqrt{\left(\frac{5}{6}\right)^2}=\frac{2}{3}-\frac{5}{6}=-\frac{1}{6}\)

ẹc, mình chưa học tới bài căn bậc :V

a) \(\sqrt{0,09}-\sqrt{0,64}=\frac{-1}{2}=-0,5\)

b) \(0,1\cdot\sqrt{225}-\sqrt{\frac{1}{4}}=0,1\cdot15-\frac{1}{2}=1\)

c) \(\sqrt{0,36}\cdot\sqrt{\frac{25}{16}+\frac{1}{4}}=\frac{3\sqrt{29}}{20}\)

d) đề baì có sai ko ban?

\(M=|-5+2\frac{1}{2}|+3\frac{1}{2}-\sqrt{0,49}\)
\(M=|-5+\frac{5}{2}|+\frac{7}{2}-\frac{7}{10}\)
\(M=|-\frac{5}{2}|+\frac{7}{2}-\frac{7}{10}\)
\(M=\frac{5}{2}+\frac{7}{2}-\frac{7}{10}\)
\(M=\frac{25}{10}+\frac{35}{10}-\frac{7}{10}\)
\(M=\frac{25+35-7}{10}\)
\(M=\frac{53}{10}\)
\(V\text{ậy}M=\frac{53}{10}\)
HỌC TỐT

\(\begin{array}{l}0,49 = {\left( {0,7} \right)^2};\\\,\frac{1}{{32}} =\frac{1^5}{2^5}={\left( {\frac{1}{2}} \right)^5};\\\,\frac{{ - 8}}{{125}} =\frac{(-2)^3}{5^3}= {\left( {\frac{{ - 2}}{5}} \right)^3};\end{array}\)

\(\frac{{16}}{{81}} =\frac{4^2}{9^2}= {\left( {\frac{4}{9}} \right)^2} (hoặc \,\frac{{16}}{{81}} =\frac{2^4}{3^4}= {\left( {\frac{2}{3}} \right)^4});\\\,\frac{{121}}{{169}} =\frac{11^2}{13^2}= {\left( {\frac{{11}}{{13}}} \right)^2}\)

\(b,\left(\sqrt{1\frac{9}{16}-\sqrt{\frac{9}{16}}}\right):5\)

\(=\left(\sqrt{\frac{25}{16}-\frac{3}{4}}\right):5\)

\(=\sqrt{\frac{13}{16}}:5\)

\(=\frac{\sqrt{13}}{4}:5\)

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