a)\(0,2:1\frac{3}{5}+80\%=\frac{1}{8}+80\%=\frac{3205}{32}\)

b)\(0,5:\frac{5}{4}-2\frac{1}{5}=\frac{2}{5}-\frac{11}{5}=-\frac{9}{5}\)

\(0,2:1\frac{3}{5}+80\%=\left(\frac{2}{10}+\frac{8}{5}\right)+80\%=\left(\frac{20}{100}+\frac{160}{100}\right)+80\%=\frac{180}{100}+80\%=180\%+80\%=260\%\)

a,    6/7+5/9+8/7-2/9=(6/7+8/7)+(5/9-2/9)=14/7+3/9=2+1/3=7/3

b, 5+7/3=22/3

a/ \(\frac{6}{7}+\frac{5}{9}+\frac{8}{7}-\frac{2}{9}\)

= \(\left(\frac{6}{7}+\frac{8}{7}\right)+\left(\frac{5}{9}-\frac{2}{9}\right)\)

=  \(2+\frac{1}{3}\)

= \(\frac{7}{3}\)

b/ 5+\(2\frac{1}{3}\)

= 5 + \(\frac{7}{3}\)

= \(\frac{22}{3}\)

a) = \(\frac{7}{3}\)x 3

      =7

\(2\frac{1}{3}.3\)

\(=\left(2+\frac{1}{3}\right).3\)

\(=6+1\)

\(=7\)

Học tốt

a; (-2,5.0,38.0,4) - {0,125.3,15.(-8)}

= (-2.5.0,4).0,38 - {-8.0,125.3,15}

= - 1.0,38 - {-1.3,15}

= -0,38 + 3,15

= 2,77

b; {(-20,83).0,2 + (-9,17).0,2 : {2,47.0,5 - (-3,53.0,5}

= {0,2.(-20,83 - 9,17)}: {0,5.(2,47 + 3,53)}

= {- 0,2.30}:{0,5.6}

= - 6:6 : 0,5

= -1 : 0,5

= - 2 

\(125\%\cdot\left(-\frac{1}{2}\right)^2\div\left(1\frac{5}{6}-1,5\right)+2016^0\)

\(=\frac{125}{100}\cdot\frac{1}{4}\div\left(\frac{11}{6}-\frac{3}{2}\right)+1\)

\(=\frac{5}{4}\cdot\frac{1}{4}\div\left(\frac{11}{6}-\frac{9}{6}\right)+1\)

\(=\frac{5}{16}\div\frac{2}{6}+1\)

\(=\frac{15}{16}+1=\frac{31}{16}\)

         \(125\%.\left(\frac{-1}{2}\right)^2:\left(1\frac{5}{6}-1,5\right)+2016^0\)

\(=\frac{125}{100}.\frac{1}{4}:\left(\frac{11}{6}-\frac{3}{2}\right)+1\)

\(=\frac{5}{16}:\left(\frac{11}{6}-\frac{9}{6}\right)+1\)

\(=\frac{5}{16} :\frac{1}{3}+1\)

\(=\frac{5}{16} .\frac{3}{1}+1\)

\(=\frac{15}{16}+1\)

\(=\frac{31}{16}\)

\(N=-2\frac{2}{3}-0,2+1,75-\frac{5}{6}+0,7\)

\(N=\frac{-8}{3}-\frac{1}{5}+\frac{7}{4}-\frac{5}{6}+\frac{7}{10}\)

\(N=\frac{-160}{60}-\frac{12}{60}+\frac{105}{60}-\frac{50}{60}+\frac{42}{60}\)

\(N=\frac{\left[\left(-160\right)-12+105-50=42\right]}{60}\)

\(N=\frac{-75}{60}=\frac{-5}{4}\)

\(\Rightarrow N=\frac{-5}{4}\)

= -8/3 - 1/5 + 7/4 - 5/6 + 7/10 =

= -43/15 + 11/12 + 7/10 =

= -39/20 + 7/10 =

= -5/4

tk cho mình nhé bạn

= 16 . 5 - 131 + 13 - 16 

= 16 . 5 - 16 + 13 - 131

= 16 . 4 + 13 - 131

= 64 + 13 - 131

= 77 - 131

= -54

=80-(131+3)

=80-134

=-54

sao dể zữ vậy

thì khúc này \(\frac{3^{12}.2\left(3+2\right)}{3^{12}.2}\)

Ta thấy Tử và mẫu có \(3^{12}.2\)chung nên ta rút gọn cho nhau thì còn lại \(3+2=5\)

\(\frac{3^{13}.2+3^{12}.2^2}{3^{12}.2}=\frac{3^{12}.2\left(3+2\right)}{3^{12}.2}=3+2=5\)

\(\frac{3}{1.4}+\frac{5}{4.9}+\frac{7}{9.16}+\frac{15}{16.31}\)

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{16}+\frac{1}{16}-\frac{1}{31}\)

\(=1-\frac{1}{31}\)

\(=\frac{30}{31}\)

Dựa vào công thức được chứng minh:

(Em có thể chứng minh lại)

Ta có:

\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{16}+\frac{1}{16}-\frac{1}{31}\)

\(=1-\frac{1}{31}\)

\(=\frac{30}{31}\)

Chúc em học tốt^^