A=1

bấm máy tính cx thấy mệt luôn!!!

kết quả là 1 nha, bn có thể tính nhẩm sẽ ra nhanh thôi

( chúc bạn học tốt)

A=\(\left[\dfrac{\dfrac{42}{31}.\dfrac{31}{7}-\left(15-\dfrac{2}{3}\right)}{\dfrac{29}{6}+\dfrac{1}{6}.\dfrac{20}{3}}\right].\dfrac{31}{50}\)

= \(\left(\dfrac{6-\dfrac{43}{3}}{\dfrac{29}{6}+\dfrac{10}{9}}\right).\dfrac{31}{50}\)=\(\left(\dfrac{\dfrac{-25}{3}}{\dfrac{107}{18}}\right).\dfrac{31}{50}\)=\(\dfrac{-150}{107}.\dfrac{31}{50}\)=\(\dfrac{-93}{107}\)

\(\text{a) }\left|2-5x\right|=\left|3x+1\right|\\ \Leftrightarrow\left[{}\begin{matrix}2-5x=3x+1\\2-5x=-3x-1\end{matrix}\right. \Leftrightarrow\left[{}\begin{matrix}-5x-3x=1-2\\-5x+3x=-1-2\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}-8x=-1\\-2x=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{8}\\x=\dfrac{3}{2}\end{matrix}\right.\)

Vậy tập nghiệm phương trình là \(S=\left\{\dfrac{1}{8};\dfrac{3}{2}\right\}\)

\(\text{b) }\dfrac{3}{4x-20}+\dfrac{15}{50-2x^2}+\dfrac{7}{6x+30}=0\)

ĐXKĐ của phương trình \(:x\ne\pm5\)

\(\text{Ta có }:\dfrac{3}{4x-20}+\dfrac{15}{50-2x^2}+\dfrac{7}{6x+30}=0\\ \Rightarrow\dfrac{3}{4\left(x-5\right)}+\dfrac{15}{2\left(25-x^2\right)}+\dfrac{7}{6\left(x+5\right)}=0\\ \Rightarrow\dfrac{3}{4\left(x-5\right)}-\dfrac{15}{2\left(x+5\right)\left(x-5\right)}+\dfrac{7}{6\left(x+5\right)}=0\\ \Rightarrow\dfrac{9\left(x+5\right)}{12\left(x+5\right)\left(x-5\right)}-\dfrac{90}{12\left(x+5\right)\left(x-5\right)}+\dfrac{14\left(x-5\right)}{12\left(x+5\right)\left(x-5\right)}=0\\ \Rightarrow9x+45-90+14x-70=0\\ \Leftrightarrow23x=115\\ \Leftrightarrow x=5\left(KTM\right)\)

Vậy phương trình vô nghiệm

\(\text{c) }\dfrac{x+29}{31}-\dfrac{x+27}{33}=\dfrac{x+17}{43}-\dfrac{x+15}{45}\\ \Leftrightarrow\left(\dfrac{x+29}{31}+1\right)-\left(\dfrac{x+27}{33}+1\right)=\left(\dfrac{x+17}{43}+1\right)-\left(\dfrac{x+15}{45}+1\right)\\ \Leftrightarrow\dfrac{x+60}{31}-\dfrac{x+60}{33}-\dfrac{x+60}{43}+\dfrac{x+60}{45}=0\\ \Leftrightarrow\left(x+60\right)\left(\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\right)=0\\ \Leftrightarrow x+60=0\left(\text{Vì }\dfrac{1}{31}-\dfrac{1}{33}-\dfrac{1}{43}+\dfrac{1}{45}\ne0\right)\\ \Leftrightarrow x=-60\)

Vậy \(x=-60\) là nghiệm của phương trình

=\(\dfrac{11}{31}\)*\(\left(\dfrac{-2}{17}-\dfrac{-9}{17}\right)\)+\(\dfrac{7}{31}\)*\(\dfrac{-20}{17}\)

=\(\dfrac{11}{31}\)*\(\dfrac{-7}{17}\)+\(\dfrac{7}{31}\)*\(\dfrac{-20}{17}\)

=\(\dfrac{-77}{512}\)+\(\dfrac{-140}{512}\)

=\(\dfrac{-217}{512}\)

nhanh giúp mk với

=\(\dfrac{4}{2}\)=2

2

2

\(\dfrac{4}{3}+\dfrac{-11}{31}+\dfrac{3}{10}-\dfrac{20}{31}-\dfrac{2}{5}\)

\(=\dfrac{4}{3}+\left(\dfrac{-11}{31}+\dfrac{-20}{31}\right)+\left(\dfrac{3}{10}-\dfrac{2}{5}\right)\)

\(=\dfrac{4}{3}+-1+\dfrac{-1}{10}\)

\(=\dfrac{1}{3}+\dfrac{-1}{10}\)

\(=\dfrac{7}{30}\)

Chúc bạn học tốt

= 91/93 + -107/310 - 2/5

= 19/30 - 2/5

= 7/30

= 4/3 -11/31 +  3/10 - 20/31 - 2/5

= 4/3 +3/10 - 2/5 +(-11/31 - 20/31)

= 37/30 -1 = 7/30 

=\(-\dfrac{54}{25}\)

\(=\left[\left(-\dfrac{3}{31}\right)+\left(-\dfrac{28}{31}\right)\right]+\left[\left(-\dfrac{6}{17}\right)+\left(-\dfrac{11}{17}\right)\right]+\left[\dfrac{1}{25}+\left(-\dfrac{1}{5}\right)\right]\)

\(=\left(-1\right)+\left(-1\right)+\left[\dfrac{1}{25}+\left(-\dfrac{5}{25}\right)\right]\)

\(=\left(-1\right)+\left(-1\right)+\left(-\dfrac{4}{25}\right)\)

\(=\left(-2\right)+\left(-\dfrac{4}{25}\right)\)

\(=\left(-\dfrac{50}{25}\right)+\left(-\dfrac{4}{25}\right)\)

\(=-\dfrac{54}{25}\)

\(=\left(\dfrac{-3}{31}+\dfrac{-28}{31}\right)+\left(\dfrac{-6}{17}+\dfrac{-11}{17}\right)+\left(\dfrac{1}{25}+\dfrac{1}{5}\right)\)

\(=-1+-1+\left(\dfrac{1}{25}+\dfrac{-5}{25}\right)\)

\(=-2\)\(+\dfrac{-4}{25}\)

\(=\)\(\dfrac{50}{25}+\dfrac{-4}{25}\)

=\(\dfrac{46}{25}\)