21x²-14x-2x²+x-2x-5>0
19x²-15x-5>0
19x²-15x-5=0
D=15² -4*19*(-5)=225+380=605
x₁=(15-√605)/38
x₂=(15+√605)/38
+ - +
--------- (15-√605)/38 ----------------- (15+√605)/38 --------------
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x∈(-∞; (15-√605)/38)U(15+√605)/38; +∞)