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\(...=-\dfrac{4}{7}-\dfrac{3}{11}+\dfrac{3}{11}-\dfrac{3}{7}=-\dfrac{4}{7}-\dfrac{3}{7}=-1\)
-(4/7 + 3/11) - (-3/11 + 3/7)
= (-4/7) + (-3/11) - (-3/11) - 3/7
= [(-4/7) - 3/7)] + [(-3/11) - (-3/11)]
= -1 + 0
= -1
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Đặt \(A=1992\cdot19911991-1991\cdot19921992\)
\(\Rightarrow A=1992\cdot\left(1991\cdot10001\right)-1991\cdot\left(1992\cdot10001\right)\)
\(\Rightarrow A=1992\cdot1991\cdot10001-1991\cdot1992\cdot10001=0\)
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\(=\dfrac{2011}{2012}\cdot\left(3-3-\dfrac{2011}{2012}\right)-\dfrac{1}{2012}\cdot\dfrac{2011}{2012}\)
\(=\dfrac{2011}{2012}\cdot\left(-\dfrac{2011}{2012}\right)-\dfrac{1}{2012}\cdot\dfrac{2011}{2012}\)
\(=\dfrac{2011}{2012}\cdot\left(\dfrac{-2011}{2012}-\dfrac{1}{2012}\right)\)
\(=\dfrac{2011}{2012}\cdot\left(-1\right)\)
\(=-\dfrac{2011}{2012}\)
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\(B=\dfrac{\dfrac{5-10\sqrt{2}+6\sqrt{2}}{70}\cdot\left(-\dfrac{4}{15}\right)}{\dfrac{5+6\sqrt{2}-10\sqrt{2}}{50}\cdot\dfrac{5}{7}}=\dfrac{10-8\sqrt{2}}{525}:\dfrac{5-4\sqrt{2}}{70}\\ B=\dfrac{2\left(5-4\sqrt{2}\right)}{525}\cdot\dfrac{70}{5-4\sqrt{2}}=\dfrac{4}{15}\)
= 4396
dung khong ?
\(16\cdot54+18\cdot68+64\cdot58\)
\(=16\cdot54+18\cdot68+16\cdot4\cdot58\)
\(=16\cdot\left(54+4+58\right)+18\cdot68\)
\(=16\cdot116+18\cdot68\)
\(=1856+1224\)
\(=3080\)