Câu 138 trang 33 Sách Bài Tập (SBT) Toán lớp 7 tập 1
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(E = {{left( {13{1 over 4} - 2{5 over {27}} - 10{5 over 6}} ight).230{1 over {25}} + 46{3 over 4}} over {left( {1{3 over 7} + {{10} over 3}} ight):left( {12{1 over 3} - 14{2 over 7}} ight)}})
Giải
(E = {{left( {13{1 over 4} - 2{5 over {27}} - 10{5 over 6}} ight).230{1 over {25}} + 46{3 over 4}} over {left( {1{3 over 7} + {{10} over 3}} ight):left( {12{1 over 3} - 14{2 over 7}} ight)}})
(eqalign{
& = {{left( {13 - 2 - 10 + {1 over 4} - {5 over {27}} - {5 over 6}}
ight).{{5771} over {25}} + {{187} over 4}} over {left( {{{30} over {21}} + {{70} over {21}}}
ight):left( {{{259} over {21}} - {{300} over {21}}}
ight)}} cr
& = {{left( {1 + {{27 - 20 - 90} over {108}}}
ight).{{5751} over {25}} + {{187} over 4}} over {{{100} over {21}}:{{ - 41} over {21}}}} cr} )
(eqalign{
& = {{left( {{{108} over {108}} - {{83} over {108}}}
ight).{{5751} over {25}} + {{187} over 4}} over {{{100} over {21}}.{{ - 21} over {41}}}} cr
& = {{{{25} over {108}}.{{5751} over {25}} + {{187} over 4}} over {{{ - 100} over {41}}}} cr
& = left( {{{213} over 4} + {{187} over 4}}
ight).{{ - 41} over {100}} = 100.{{ - 41} over {100}} cr} )
= -41
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