tìm a, b thỏa mãn
a, -19/2<a<-20/3
b, 1/3<4/b<1/2
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\(1,\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\1-2x=5\end{matrix}\right.\Leftrightarrow D\\ 2,\Leftrightarrow\left(-3\right)^x=-27\cdot81=-2187=\left(-3\right)^7\\ \Leftrightarrow x=7\left(A\right)\)
a: \(\Leftrightarrow\left(x;y-3\right)\in\left\{\left(1;17\right);\left(17;1\right);\left(-1;-17\right);\left(-17;-1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(1;20\right);\left(17;4\right);\left(-1;-14\right);\left(-17;2\right)\right\}\)
b: \(\Leftrightarrow\left(x-1;y+2\right)\in\left\{\left(1;7\right);\left(7;1\right);\left(-1;-7\right);\left(-7;-1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(2;5\right);\left(8;-1\right);\left(0;-9\right);\left(-6;-3\right)\right\}\)
c: =>(y+1)(3x+1)=7
=>\(\left(3x+1;y+1\right)\in\left\{\left(1;7\right);\left(7;1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(0;6\right);\left(2;0\right)\right\}\)
\(a,x\in\left\{-2;-1;0;1\right\}\\ \Rightarrow\text{Tổng là }-2-1+0+1=-2\\ b,x\in\left\{-2020;-2019;...;2020\right\}\\ \Rightarrow\text{Tổng là }-2020-2019-...-0+1+...+2020\\ =\left(-2020+2020\right)+\left(-2019+2019\right)+...+\left(-1+1\right)-0=0\)