X^3+x^2-9x-9=0 ; 2x^3+8x=x^2+4 ; 3x^3 - x^2 + 18x-6=0 - вопрос №7501732990238243321860 от mrnikes2016 19.03.2020 14:48

Question

Алгебра: X^3+x^2-9x-9=0 ; 2x^3+8x=x^2+4 ; 3x^3 - x^2 + 18x-6=0

mrnikes2016 · Answer

X^3 + x^2 - 9x - 9 = 0
x^2 (x + 1) - 9(x + 1) = 0
(x^2 - 9)(x + 1) = 0

x + 1 = 0
x₁ = - 1

x^2 - 9 = 0
x^2 = 9
x₂ = - 3
x₃ = 3

2x^3 + 8x - x^2 - 4 = 0
2x (x^2 + 4) - 1(x^2 + 4) = 0
(x^2 + 4)(2x - 1) = 0

x^2 + 4 = 0
x^2 = - 4
==> ∅

2x - 1 = 0
2x = 1
x = 0,5

3x^3 - x^2 + 18x - 6 = 0
x^2 (3x - 1) + 6(3x - 1) = 0
(3x - 1)(x^2 + 6) = 0

x^2 + 6 = 0
x^2 = - 6
x ==> ∅

3x - 1 = 0
3x = 1
x = 1/3