x²-x-2≤0

x²-x-2≤0 Δ=1-4*1*(-2) Δ=9 √Δ=3 x1=-2/2=-1 x2=4/2=2 x∈<-1,2>

x²-x-2≤0 Δ=b²-4ac Δ=(-1)²-4*1*(-2)=1+8=9 √Δ=3 x₁=-b+√Δ/2a=1+3/2=4/2=2 x₂=-b-√Δ/2a=1-3/2=-2/2=-1 x∈<-1;2>