Rút gọn các biểu thức ( chú ý đến thứ tự thực hiện các phép tính) :
a. \({{x + 1} \over {x + 2}}:{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}\)
b. \({{x + 1} \over {x + 2}}:\left( {{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}} \right)\)
c. \({{x + 1} \over {x + 2}}.{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}\)
d. \({{x + 1} \over {x + 2}}.\left( {{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}} \right)\)
e. \({{x + 1} \over {x + 2}}:{{x + 2} \over {x + 3}}.{{x + 3} \over {x + 1}}\)
f. \({{x + 1} \over {x + 2}}:\left( {{{x + 2} \over {x + 3}}.{{x + 3} \over {x + 1}}} \right)\)
a. \({{x + 1} \over {x + 2}}:{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}\)\( = {{x + 1} \over {x + 2}}.{{x + 3} \over {x + 2}}.{{x + 1} \over {x + 3}}\)
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\( = {{\left( {x + 1} \right)\left( {x + 3} \right)\left( {x + 1} \right)} \over {\left( {x + 2} \right)\left( {x + 2} \right)\left( {x + 3} \right)}} = {{{{\left( {x + 1} \right)}^2}} \over {{{\left( {x + 2} \right)}^2}}}\)
b. \({{x + 1} \over {x + 2}}:\left( {{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}} \right)\)
\(\eqalign{ & = {{x + 1} \over {x + 2}}:\left( {{{x + 2} \over {x + 3}}.{{x + 1} \over {x + 3}}} \right) = {{x + 1} \over {x + 2}}:{{\left( {x + 2} \right)\left( {x + 1} \right)} \over {{{\left( {x + 3} \right)}^2}}} \cr & = {{x + 1} \over {x + 2}}.{{{{\left( {x + 3} \right)}^2}} \over {\left( {x + 2} \right)\left( {x + 1} \right)}} = {{{{\left( {x + 3} \right)}^2}} \over {{{\left( {x + 2} \right)}^2}}} \cr} \)
c. \({{x + 1} \over {x + 2}}.{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}\)\( = {{\left( {x + 1} \right)\left( {x + 2} \right)} \over {\left( {x + 2} \right)\left( {x + 3} \right)}}.{{x + 1} \over {x + 3}} = {{{{\left( {x + 1} \right)}^2}} \over {{{\left( {x + 3} \right)}^2}}}\)
d. \({{x + 1} \over {x + 2}}.\left( {{{x + 2} \over {x + 3}}:{{x + 3} \over {x + 1}}} \right)\)\( = {{x + 1} \over {x + 2}}.\left( {{{x + 2} \over {x + 3}}.{{x + 1} \over {x + 3}}} \right) = {{x + 1} \over {x + 2}}.{{\left( {x + 2} \right)\left( {x + 1} \right)} \over {{{\left( {x + 3} \right)}^2}}}\)
\( = {{{{\left( {x + 1} \right)}^2}} \over {{{\left( {x + 3} \right)}^2}}}\)
e. \({{x + 1} \over {x + 2}}:{{x + 2} \over {x + 3}}.{{x + 3} \over {x + 1}}\)\( = {{x + 1} \over {x + 2}}.{{x + 3} \over {x + 2}}.{{x + 3} \over {x + 1}} = {{{{\left( {x + 3} \right)}^2}} \over {{{\left( {x + 2} \right)}^2}}}\)
f. \({{x + 1} \over {x + 2}}:\left( {{{x + 2} \over {x + 3}}.{{x + 3} \over {x + 1}}} \right)\)\( = {{x + 1} \over {x + 2}}:{{x + 2} \over {x + 1}} = {{x + 1} \over {x + 2}}.{{x + 1} \over {x + 2}} = {{{{\left( {x + 1} \right)}^2}} \over {{{\left( {x + 2} \right)}^2}}}\)