{2x²+9x+7≤0
{2x+5≤0
2x²+9x+7=2(x+1)(x+3,5)
D=9²-4*2*7=81-56=25=5²
x₁=(-9+5)/4=-4/4=-1
x₂=(-9-5)/4=-14/4=-3,5
{2(x+1)(x+3,5)≤0
{2x≤-5
{(x+1)(x+3,5)≤0
{x≤-2,5
+ - +
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x∈[-3,5;-2,5]