Bài 10: Làm theo mẫu:
\(\frac{43}{15}\).=\(\frac{86}{10}\)8,6 \(\frac{9}{5}\) \(\frac{2}{25}\) \(\frac{111}{125}\) | \(\frac{23}{8}\) \(\frac{76}{4}\) \(\frac{42}{25}\) \(\frac{370}{50}\)
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\(\frac{9}{5}=\frac{18}{10}=1,8\)
\(\frac{2}{25}=\frac{8}{100}=0,08\)
\(\frac{111}{125}=\frac{888}{1000}=0.888\)
\(\frac{23}{8}=\frac{2875}{1000}=2,875\)
\(\frac{76}{4}=\frac{1900}{100}=19\)
\(\frac{9}{5}=\frac{18}{10}=1,8\)
\(\frac{2}{25}=\frac{8}{100}=0,08\)
\(\frac{111}{125}=\frac{111.8}{125.8}=\frac{888}{1000}=0,888\)
\(\frac{76}{4}=19\)
\(\frac{23}{8}=\frac{23.125}{8.125}=\frac{2875}{1000}=2,875\)
\(\frac{42}{25}=\frac{42.4}{25.4}=\frac{168}{100}=1,68\)
\(\frac{370}{50}=\frac{37}{5}=\frac{37.2}{5.2}=\frac{74}{10}=7,4\)
2/25=4/50=0,08
111/125=222/250=0,888
23/8=46/16=2,875 76/4=152/8=19 42/25=84/50=1,68 370/50=740/100=7,4
2/25=4/50=0,08
111/125=222/250=0,888
23/8=46/16=2,875 76/4=152/8=19 42/25=84/50=1,68 370/50=740/100=7,4
2/25=8/100=0,08
111/125=888/1000=0,888
23/8=2875/1000=2,875
76/4=1900/100=19
42/25=168/100=1,68
370/50=740/100=7,4
2/25=8/100=0,8
111/125=888/1000=0,888
23/8=2875/1000=2,875
76/4=1900/100=1,9
42/25=168/100=1,68
370/50=740/100=7,4
a, Câu hỏi của Nguyễn Ánh Ngân - Toán lớp 6 - Học toán với OnlineMath
b, Câu hỏi của Vũ Xuân Hiếu - Toán lớp 6 | Học trực tuyến
c)
a) Ta có: \(\frac{x-91}{37}+\frac{x-86}{42}+\frac{x-78}{50}+\frac{x-49}{79}=4\)
\(\Leftrightarrow\frac{x-91}{37}-1+\frac{x-86}{42}-1+\frac{x-78}{50}-1+\frac{x-49}{79}-1=0\)
\(\Leftrightarrow\frac{x-91-37}{37}+\frac{x-86-42}{42}+\frac{x-78-50}{50}+\frac{x-49-79}{79}=0\)
\(\Leftrightarrow\frac{x-128}{37}+\frac{x-128}{42}+\frac{x-128}{50}+\frac{x-128}{79}=0\)
\(\Leftrightarrow\left(x-128\right)\left(\frac{1}{37}+\frac{1}{42}+\frac{1}{50}+\frac{1}{79}\right)=0\)
Vì \(\frac{1}{37}+\frac{1}{42}+\frac{1}{50}+\frac{1}{79}>0\)
nên x-128=0
hay x=128
Vậy: x=128
b) Ta có: \(\frac{x-29}{1970}+\frac{x-27}{1972}+\frac{x-25}{1974}+\frac{x-23}{1976}+\frac{x-1970}{29}+\frac{x-1972}{27}+\frac{x-1974}{25}+\frac{x-1976}{23}-8=0\)
\(\Leftrightarrow\frac{x-29}{1970}-1+\frac{x-27}{1972}-1+\frac{x-25}{1974}-1+\frac{x-23}{1976}-1+\frac{x-1970}{29}-1+\frac{x-1972}{27}-1+\frac{x-1974}{25}-1+\frac{x-1976}{23}-1=0\)
\(\Leftrightarrow\frac{x-29-1970}{1970}+\frac{x-27-1972}{1972}+\frac{x-25-1974}{1974}+\frac{x-23-1976}{1976}+\frac{x-1970-29}{29}+\frac{x-1972-27}{27}+\frac{x-1974-25}{25}+\frac{x-1976-23}{23}=0\)
\(\Leftrightarrow\left(x-1999\right)\left(\frac{1}{1970}+\frac{1}{1972}+\frac{1}{1974}+\frac{1}{1976}+\frac{1}{29}+\frac{1}{27}+\frac{1}{25}+\frac{1}{23}\right)=0\)
Vì \(\frac{1}{1970}+\frac{1}{1972}+\frac{1}{1974}+\frac{1}{1976}+\frac{1}{29}+\frac{1}{27}+\frac{1}{25}+\frac{1}{23}>0\)
nên x-1999=0
hay x=1999
Vậy: x=1999
a) Ta có \(\frac{x-91}{37}+\frac{x-86}{42}+\frac{x-78}{50}+\frac{x-49}{79}\)=4
<=>\(\frac{x-91}{37}+\frac{x-86}{42}+\frac{x-78}{50}+\frac{x-49}{79}-4=0\)
<=>\(\frac{x-91}{37}-1+\frac{x-86}{42}-1+\frac{x-78}{50}-1+\frac{x-49}{79}-1=0\)
<=>\(\frac{x-128}{37}+\frac{x-128}{42}+\frac{x-128}{50}+\frac{x-128}{79}=0\)
<=>(x-128)\(\left(\frac{1}{37}+\frac{1}{42}+\frac{1}{50}+\frac{1}{79}\right)=0\)
Vì \(\frac{1}{37}+\frac{1}{42}+\frac{1}{50}+\frac{1}{79}>0\)=>x-128=0<=>x=128
b)Tương tự
<=>x-128=0
<=>x=128
Chú ý \(\frac{1}{37}+\frac{1}{42}+\frac{1}{50}+\frac{1}{79}\)>0
b)tương tự
3) C thiếu đề
4) \(D=\frac{1}{9}-\left|\frac{-5}{23}\right|-\left(\frac{-5}{23}+\frac{1}{9}+\frac{25}{7}\right)+\frac{50}{4}-\frac{7}{30}\)
\(D=\frac{1}{9}-\frac{5}{23}+\frac{5}{23}-\frac{1}{9}-\frac{25}{7}+\frac{50}{4}-\frac{7}{30}\)
\(D=\frac{1}{9}-\frac{1}{9}-\frac{5}{23}+\frac{5}{23}+\frac{-25}{7}+\frac{50}{4}-\frac{7}{30}\)
\(D=0+0+\frac{125}{14}-\frac{7}{30}\)
\(D=\frac{913}{105}\)