tìm x thuộc Z
-(-432-5x+98)+(-432-679-3x)-(-431+x-679)=-(-1+78)
765-(-974+2x)=-346
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a/\(-\left(-432-3x\right)+\left(-432-4x+21\right)=-2345\)
\(\Leftrightarrow+432+3x-432-4x+21=-2345\)\(\Leftrightarrow\left[432+\left(-432\right)\right]+\left[\left(-4x\right)+3x\right]+21=-2345\)
\(\Leftrightarrow0+-1x+21=-2345\)\(\Leftrightarrow-1x=-2345-21=-2366\)
\(\Rightarrow x=\left(-2366\right):\left(-1\right)=2366\)
b/\(12x-\left(-3546-3x\right)=\left(2x-234\right)-\left(-678-2x\right)\)
\(\Leftrightarrow12x+3546+3x=2x-234+678+2x\)
\(\Leftrightarrow15x+3546=\left(2x+2x\right)+\left[\left(-234\right)+678\right]\)
\(\Leftrightarrow15x+3546=4x+444\)
\(\Leftrightarrow15x+3546-4x-444=0\)
\(\Leftrightarrow\left(15x-4x\right)+\left(3546-444\right)=0\)
\(\Leftrightarrow11x+3102=0\)
\(\Leftrightarrow11x=0-3102=-3102\)
\(\Rightarrow x=\left(-3102\right):11=-282\)
\(a,564\times8-64\times4\times2=564\times8-64\times8=8\times\left(564-64\right)=8\times500=4000\\ b,37\times18-9\times74+100\\ =37\times2\times9-9\times74+100\\ =\left(74\times9-9\times74\right)+100=0+100=100\\ c,679\times78+679\times23-679=679\times\left(78+23-1\right)\\ =679\times100\\ =67900\)
[1 x 2 x 3 x 4 x........................x100] x [679+679 x 123-679 x124]
= A x [679 x 124-679 x 124]
= A x 0
=0