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\(A=-5,13:\left(5\frac{5}{28}-1\frac{8}{9}.1,25+1\frac{16}{63}\right)\)
\(A=-5,13:\left(5\frac{5}{28}-\frac{85}{36}+1\frac{16}{63}\right)\)
\(A=-5,13:\frac{57}{14}=-\frac{63}{50}\)
\(B=\left(3\frac{1}{3}.1,9+19,5:4\frac{1}{3}\right).\left(\frac{62}{72}-\frac{4}{25}\right)\)
\(B=\left(\frac{19}{3}+\frac{9}{2}\right).\frac{631}{900}\)
\(B=\frac{65}{6}.\frac{631}{900}=\frac{8203}{1080}\)
A= 6 - 2/3 +1/2 -5 -5/3 + 3/2 - 3 + 7/3 -5/2
A = 6- 5 - 3 - 2/3 -5/3 +7/3 +1/2 + 3/2 -5/2
A= -2 +0 - 1/2
A= -5/2
\(a)\) Ta có :
\(\frac{x}{18}=\frac{y}{9}\)\(\Leftrightarrow\)\(\frac{x}{2}=y\)
\(\Rightarrow\)\(x=2y\)
Thay \(x=2y\) vào \(A=\frac{2x-3y}{2x+3y}\) ta được :
\(A=\frac{2.2y-3y}{2.2y+3y}=\frac{4y-3y}{4y+3y}=\frac{y}{7y}=\frac{1}{7}\)
Vậy ... ( tự kết luận )
Chúc bạn học tốt ~
Cách 1:
\(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)
=\(\frac{35}{6}-\frac{31}{6}-\frac{19}{6}\)
=\(\frac{35-31-19}{6}\)
=\(-\frac{15}{6}=-\frac{5}{2}\)
Cách 2:
\(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)
=\(6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)
=\(\left(-\frac{2}{3}-\frac{5}{3}+\frac{7}{3}\right)+\left(\frac{1}{2}+\frac{3}{2}-\frac{5}{2}\right)+\left(6-5-3\right)\)
=\(0-\frac{1}{2}-2\)
=\(-\frac{5}{2}\)
Có : a/ab+a+1 = a/ab+a+abc = 1/b+1+bc = 1/bc+b+1
c/ca+c+1 = bc/abc+bc+b = b/1+bc+b = b/bc+b+1
=> A = 1+bc+b/bc+b+1 = 1
Tk mk nha
BÀI 1:
\(\frac{a}{ab+a+1}+\frac{b}{bc+b+1}+\frac{c}{ca+c+1}\)
\(=\frac{a}{ab+a+1}+\frac{ab}{a\left(bc+b+1\right)}+\frac{abc}{ab\left(ca+c+1\right)}\)
\(=\frac{a}{ab+a+1}+\frac{ab}{abc+ab+a} +\frac{abc}{a^2bc+abc+ab}\)
\(=\frac{a}{ab+a+1}+\frac{ab}{ab+a+1}+\frac{1}{ab+a+1}\) (thay abc = 1)
\(=\frac{a+ab+1}{a+ab+1}=1\)
số cần tìm là :
\(\frac{1}{2}+\frac{3}{28}+\frac{2}{8}+\frac{4}{77}+\frac{5}{176}\)
= \(\frac{1935}{2128}\)
\(\frac{1}{2}+\frac{2}{8}+\frac{3}{28}+\frac{4}{77}+\frac{5}{176}=\frac{15}{16}\)