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a)x²≥25
x≥5 ∧ x ≤-5
x∈(-oo,-5>u<5,+oo)
b)x²≤16
x≤-4 ∧ x≥4
x∈<-4,4>
c)x²-x≥6
x²-x-6≥0
Δ=1+24=25⇒√Δ=5
x1=(1-5)/2=-2
x2=(1+5)/2=3
x∈(-oo,-2>u<3,+oo)
d)x²-4≤3x
x²-3x-4≤0
Δ=9+16=25⇒√Δ=5
x1=(3-5)/2=-1
x2=(3+5)/2=4
x∈<-1,5>
e)4x+5>x²
x²-4x-5<0
Δ=16+20=36⇒√Δ=6
x1=(4-6)/2=-1
x2=(4+6)/2=5
x∈(-1,5)
f)2x²+5x>3
2x²+5x-3>0
Δ=25+24=49⇒√Δ=7
x1=(-5-7)/4=-3
x2=(-5+7)/4=1/2
x∈(-oo,-3)u(1/2,+oo)