Proszę rozwiązać:
5x³+21x²-21x-5=0
5(x³-1)+21x(x-1)=0
5(x-1)(x²+x+1) + 21x(x-1)=0
(x-1)[5(x²+x+1)+21x]=0
(x-1)(5x²+5x+5+21x)=0
(x-1)(5x²+26x+5)=0
x-1=0 ∨ 5x²+26x+5=0
x=1
Δ=676-100=576
√Δ=24
x₁=(-26+24)/10 = -0,2
x₂=(-26-24)/10=-5
x=1 ∨ x=-0,2 ∨ x=-5
Z={-5; -0,2; 1}
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5x³+21x²-21x-5=0
5(x³-1)+21x(x-1)=0
5(x-1)(x²+x+1) + 21x(x-1)=0
(x-1)[5(x²+x+1)+21x]=0
(x-1)(5x²+5x+5+21x)=0
(x-1)(5x²+26x+5)=0
x-1=0 ∨ 5x²+26x+5=0
x=1
Δ=676-100=576
√Δ=24
x₁=(-26+24)/10 = -0,2
x₂=(-26-24)/10=-5
x=1 ∨ x=-0,2 ∨ x=-5
Z={-5; -0,2; 1}