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a) \(\frac{1}{3}+\frac{3}{35}< \frac{x}{210}< \frac{7}{7}+\frac{3}{5}+\frac{1}{3}\)
\(\Rightarrow\frac{44}{105}< \frac{x}{210}< \frac{29}{15}\)
\(\Rightarrow\frac{88}{210}< \frac{x}{210}< \frac{406}{210}\)
\(\Rightarrow x\in\left\{89;90;91;...;405\right\}\)
b) \(\frac{5}{3}+-\frac{14}{3}< x< \frac{8}{5}+\frac{8}{10}\)
\(\Rightarrow-3< x< 2\frac{2}{5}\)
=> x thuộc {-2;-1;0;1;2} ( nếu x là số nguyên)
\(b.\frac{1}{3}+\frac{3}{35}< \frac{x}{210}< \frac{4}{7}+\frac{3}{5}+\frac{1}{3}\)
\(\Leftrightarrow\frac{35+9}{105}< \frac{x}{210}< \frac{60+63+35}{105}\)
\(\Leftrightarrow\frac{44}{105}< \frac{x}{210}< \frac{158}{105}\)
\(\Leftrightarrow\frac{88}{210}< \frac{x}{210}< \frac{316}{210}\)
Suy ra \(x\in\left\{89;90;100;...;313;314;315\right\}\)
\(c.\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{19.21}\right)-x+\frac{221}{231}=\frac{4}{3}\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right)-x+\frac{221}{231}=\frac{4}{3}\)
\(\Leftrightarrow\frac{1}{11}-\frac{1}{21}-x+\frac{221}{231}=\frac{4}{3}\)
\(\Leftrightarrow\frac{21-11-231x+221}{231}=\frac{308}{231}\)
\(\Leftrightarrow-231x=308-21+11-221\)
\(\Leftrightarrow-231x=77\)
\(\Leftrightarrow x=-\frac{77}{231}=-\frac{1}{3}\)
^^
1. \(\frac{-7}{12}\)< \(\frac{x-1}{4}\)< \(\frac{2}{3}\)
=> \(\frac{-7}{12}\)< \(\frac{3.\left(x-1\right)}{12}\)< \(\frac{8}{12}\)
=> 3 . ( x - 1 ) thuộc { - 6 ; - 5 ; - 4 ; - 3 ; - 2 ; - 1 ; 0 ; 1 ; 2 ; 3 ; 4 ; 5 ; 6 ; 7}
Lập bảng tính giá trị x , cái này dễ lên bạn tự làm nha
1/ \(-\frac{7}{12}< \frac{x-1}{4}< \frac{2}{3}\)
hay \(\frac{-7}{12}< \frac{3.\left(x-1\right)}{12}< \frac{8}{12}\)
Vậy \(-7< 3.\left(x-1\right)< 8\)
Vậy \(3.\left(x-1\right)\in\left\{-6;-5;-4;...;7\right\}\)
mà \(x\in Z\)nên \(3.\left(x-1\right)⋮3\)
Vậy \(3.\left(x-1\right)\in\left\{-6;-3;0;3;6\right\}\)
hay \(x-1\in\left\{-2;-1;0;1;2\right\}\)
tới đây dễ rồi thì làm nốt nhé, để thời gian làm mấy câu sau!
Ta có :
\(\frac{1}{3}+\frac{3}{35}=\frac{70}{210}+\frac{18}{210}=\frac{88}{210}\)
\(\frac{4}{7}+\frac{3}{5}+\frac{1}{3}=\frac{120}{210}+\frac{126}{210}+\frac{70}{210}=\frac{316}{210}\)
⇒ 88 < x < 316
\(\left(\frac{1}{2}+\frac{3}{4}-\frac{1}{3}\right):\frac{-5}{6}< x< \frac{4}{21}.\frac{4}{7}\)
\(\Rightarrow\left(\frac{6}{12}+\frac{9}{12}-\frac{4}{12}\right):\frac{-10}{12}< x< \frac{16}{147}\)
\(\Rightarrow\frac{11}{12}.\frac{-12}{10}< x< \frac{16}{147}\)
\(\Rightarrow\frac{-11}{10}< x< \frac{16}{147}\)
\(\Rightarrow\frac{-1617}{1470}< x< \frac{16}{1470}\)
\(x=\left\{-1;0\right\}\)
Có 1/3+3/35=44/105
Có 4/7+3/5+1/3=158/105
=> 44/105< x/210<158/105 MC: 210
=> 88/210< x/210< 316/210
Vậy x thuộc {89;90;91;92;...;315}
Ta có :
\(\frac{1}{3}+\frac{3}{35}< \frac{x}{210}< \frac{4}{7}+\frac{3}{5}+\frac{1}{3}\)
\(\Leftrightarrow\)\(\frac{70}{210}+\frac{18}{210}< \frac{x}{210}< \frac{120}{210}+\frac{126}{210}+\frac{70}{210}\)
\(\Leftrightarrow\)\(\frac{70+18}{210}< \frac{x}{210}< \frac{120+126+70}{210}\)
\(\Leftrightarrow\)\(\frac{88}{210}< \frac{x}{210}< \frac{316}{210}\)
\(\Leftrightarrow\)\(88< x< 316\)
\(\Rightarrow\)\(x\in\left\{89;90;91;...;314;315\right\}\)
Vậy \(x\in\left\{89;90;91;...;314;315\right\}\)
Chúc bạn học tốt ~