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\(\left(-2021\right).\left(23+76\right)-2021=\left(-2021\right).99-2021=-202100\)
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\(5,-\dfrac{2}{7}-\left(\dfrac{5}{11}-\dfrac{9}{7}\right)+\dfrac{5}{11}=-\dfrac{2}{7}-\dfrac{5}{11}+\dfrac{9}{7}+\dfrac{5}{11}=\left(-\dfrac{2}{7}+\dfrac{9}{7}\right)-\left(\dfrac{5}{11}-\dfrac{5}{11}\right)=1-0=1\\ 6,\dfrac{2}{3}+\dfrac{-2}{5}+\dfrac{-5}{6}-\dfrac{13}{10}=\left(\dfrac{4}{6}+\dfrac{-5}{6}\right)+\left(\dfrac{-4}{10}-\dfrac{13}{10}\right)=\dfrac{-1}{6}+\dfrac{-17}{10}=\dfrac{-5}{30}+\dfrac{-51}{30}=\dfrac{-56}{30}=\dfrac{-28}{15}\)
\(7,\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{4}{-9}+\dfrac{7}{15}=\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)=\left(-1\right)+1=0\\ 8,\left(\dfrac{12}{13}+7\right)-\left(-\dfrac{1}{13}+8\right)=\dfrac{12}{13}+7+\dfrac{1}{13}-8=\left(\dfrac{12}{13}+\dfrac{1}{13}\right)+\left(7-8\right)=1+\left(-1\right)=0\)
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25.8.4.28.125
= 28.(25.4).(8.125)
= 28.100.1000
= 2800.1000
= 2800000
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Tham khảo: https://hoc247.net/hoi-dap/toan-6/tinh-a-b-voi-a-34-7-13-51-13-22-85-22-37-68-37-49-faq162600.html
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\(12,25+\left(-21,37\right)-\left(14,67-21,75\right)\)
\(=12,25-21,37-14,67+21,75\)
\(=12,25+21,75-21,37-14,63-0,04\)
\(=34-36-0,04\)
= -2-0,04=-2,04
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120:{54-[50:2.(3^2-2.4)]}
= 120:{ 54-[25.(9-8)]}
= 120:{54-[25.1]}
= 120:{54-25}
= 120:29
=\(\dfrac{120}{29}\)
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Lời giải:
$2,3.45-23.14,5=2,3.45-2,3.145=2,3(45-145)=2,3.(-100)=-230$
13 x 48 + 87 x 15 + 13 x 52 + 87 x 85 = (13 x ( 48 + 52)) + 87 x (15 + 85)
= 13 x 100 + 87 x 100
= 100 x (13 + 87)
= 100 x 100
= 10000
GOODLUCK!!
13.48 + 87.15 + 13.52 + 87.85
= 13(48 + 52) + 87.(15 + 85)
= 13.100 + 87.100
= 100(13 + 87)
= 100.100
= 10000