bài 1:
1) (x+1)(2-x)-x(1-x)<2
2) (2x+1)(2-x)+x^2<2-x^2
3) 4(2x-3)>=3(3x-4)+15
4) 5x-4-(2x-9)<=5x-S
5)(2x+3)(2x-3)>4x(x+3)
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