\(\frac{4678.4679+4680.31+4648}{4680.4679-4687.4679}\)

\(=\frac{4678.4679+4679.31+(31+4648)}{4679.\left(4680-4687\right)}\)

\(=\frac{4678.4679+4679.31+4679}{4679.\left(-7\right)}\)

\(=\frac{4679.\left(4678+31+1\right)}{4679.\left(-7\right)}\)

\(=\frac{4679.4710}{4679.\left(-7\right)}=\frac{4710}{-7}=\frac{-4710}{7}\)

lp 5 chưa hok đến số âm, nhưng bài này lại ra kp âm! nên b xem lại đề giúp mk nha!
 

1.

a) \(\dfrac{5}{18}+\dfrac{4}{7}+\dfrac{13}{18}+\dfrac{3}{7}\)

\(=\left(\dfrac{5}{18}+\dfrac{13}{18}\right)+\left(\dfrac{4}{7}+\dfrac{3}{7}\right)\)

\(=1+1=2\)

b) \(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4}\)

\(=\left(\dfrac{4}{9}.\dfrac{9}{4}\right).\dfrac{5}{19}\)

\(=1.\dfrac{5}{19}=\dfrac{5}{19}\)

tik mik nha!!!

2) \(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4} =(\dfrac{4}{9}.\dfrac{9}{4}).\dfrac{5}{19} =1.\dfrac{5}{19} =\dfrac{5}{19}\)

\(\dfrac{5}{18}+\dfrac{4}{7}+\dfrac{13}{18}+\dfrac{3}{7}\)

= \(\left(\dfrac{5}{18}+\dfrac{13}{18}\right)+\left(\dfrac{4}{7}+\dfrac{3}{7}\right)\)

= 1 + 1

= 2

\(\dfrac{4}{9}.\dfrac{5}{19}.\dfrac{9}{4}\)

= \(\left(\dfrac{4}{9}.\dfrac{9}{4}\right).\dfrac{5}{19}\)

= 1 . \(\dfrac{5}{19}\)

= \(\dfrac{5}{19}\)

~ Chúc bạn học giỏi ! ~

\(x+\dfrac{4}{5.9}+\dfrac{4}{9.13}+...+\dfrac{4}{41.45}=-\dfrac{37}{45}\\ x+\left(\dfrac{1}{5}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{13}+...+\dfrac{1}{44}-\dfrac{1}{45}\right)=-\dfrac{37}{45}\\ x+\left(\dfrac{1}{5}-\dfrac{1}{45}\right)=-\dfrac{37}{45}\\ x+\dfrac{8}{45}=-\dfrac{37}{45}\\ x=-\dfrac{37}{45}-\dfrac{8}{45}\\ x=-1\)

bạn học nhà cô Phương à

Các bạn viết hẳn ra ạ

a) 1,28:0,125+1,28×0,25+1,28×1,75

=1,28x(8+0,25+1,75)

=1,28x10=12,8

b) bạn nên viết rõ ra

\(\frac{4678\times4679+4680\times31+4648}{4680\times4679-4678\times4679}\)

\(\Leftrightarrow\frac{4679\times4678+4679\times31+4679}{4679\times\left(4680-4678\right)}\)

\(=\frac{4679\times\left(4678+31+1\right)}{4679\times2}\)

\(=\frac{4679\times4710}{4679\times2}\)

\(=\frac{4710}{2}\)

\(=2355\)

\(\frac{4678\cdot4679+4680\cdot31+4648}{4680\cdot4679-4678.4679}\)=\(\frac{4678\cdot4679+\left(4680-1\right)\cdot31+4648+31}{4680\cdot4679-4678.4679}\)

=\(\frac{4678\cdot4679+4679\cdot31+4679}{4680\cdot4679-4678.4679}\)=\(\frac{\left(4678+31+1\right)\cdot4679}{\left(4680-4678\right).4679}\)=\(\frac{4710}{2}\)=2355

\(\dfrac{x+24}{1996}+\dfrac{x+25}{1995}+\dfrac{x+26}{1994}+\dfrac{x+27}{1993}+\dfrac{x+2036}{4}=0\)

\(\Rightarrow\left(\dfrac{x+24}{1996}+1\right)+\left(\dfrac{x+25}{1995}+1\right)+\left(\dfrac{x+26}{1994}+1\right)+\left(\dfrac{x+27}{1993}+1\right)+\left(\dfrac{x+2036}{4}-4\right)=0\)\(\Rightarrow\dfrac{x+2020}{1996}+\dfrac{x+2020}{1995}+\dfrac{x+2020}{1994}+\dfrac{x+2020}{1993}+\dfrac{x+2020}{4}=0\)\(\Rightarrow\left(x+2020\right)\left(\dfrac{1}{9996}+\dfrac{1}{1995}+\dfrac{1}{1994}+\dfrac{1}{1993}+\dfrac{1}{4}\right)=0\)

\(\Rightarrow x+2020=0\Rightarrow x=-2020\)

10)\(\left(\dfrac{2x}{5}-1\right):\left(-5\right)=\dfrac{1}{4}\)

\(\dfrac{2x}{5}-1=\dfrac{1}{4}.\left(-5\right)\)

\(\dfrac{2x}{5}-1=-\dfrac{5}{4}\)

\(\dfrac{2x}{5}=-\dfrac{5}{4}+1\)

\(\dfrac{2x}{5}=-\dfrac{1}{4}\)

\(\dfrac{8x}{20}=-\dfrac{5}{20}\)

\(\Leftrightarrow8x=-5\)

\(\Rightarrow x=-5:8\)

\(x=-\dfrac{5}{8}\)

12)\(\left(3\dfrac{1}{4}:x\right).\left(-1\dfrac{1}{4}\right)=-\dfrac{5}{3}-\dfrac{5}{6}\)

\(\left(\dfrac{13}{4}:x\right).\left(-\dfrac{5}{4}\right)=-\dfrac{5}{2}\)

\(\dfrac{13}{4}:x=-\dfrac{5}{2}:\left(-\dfrac{5}{4}\right)\)

\(\dfrac{13}{4}:x=2\)

\(x=\dfrac{13}{4}:2\)

\(x=\dfrac{13}{8}\)

1) \(\left(-1\dfrac{1}{5}+x\right):\left(-3\dfrac{3}{5}\right)=\dfrac{-7}{4}+\dfrac{1}{4}:\dfrac{1}{8}\)

\(\Leftrightarrow\left(-1\dfrac{1}{5}+x\right):\left(-3\dfrac{3}{5}\right)=\dfrac{-7}{4}+2\)

\(\Leftrightarrow\left(-1\dfrac{1}{5}+x\right):\left(-3\dfrac{3}{5}\right)=\dfrac{1}{4}\)

\(\Leftrightarrow-1\dfrac{1}{5}+x=\dfrac{1}{4}.\left(-3\dfrac{3}{5}\right)\)

\(\Leftrightarrow-1\dfrac{1}{5}+x=\dfrac{1}{4}.\left(-\dfrac{18}{5}\right)\)

\(\Leftrightarrow-1\dfrac{1}{5}+x=-\dfrac{9}{10}\)

\(\Leftrightarrow x=\left(-\dfrac{9}{10}\right)-\left(-1\dfrac{1}{5}\right)\)

\(\Leftrightarrow x=\dfrac{3}{10}\)

3) \(\dfrac{3}{4}.x-\dfrac{5}{3}.x=\dfrac{7}{12}\)

\(\left(\dfrac{3}{4}-\dfrac{5}{3}\right).x=\dfrac{7}{12}\)

\(-\dfrac{11}{12}.x=\dfrac{7}{12}\)

\(x=\dfrac{7}{12}:\left(-\dfrac{11}{12}\right)\)

\(x=-\dfrac{7}{11}\)