|x^2 - 5x - 3| + |x^2 - x - 4| = 5 + |x - 2|
Сначала найдем корни в модулях:
1) x^2 - 5x - 3 = 0
D = 5^2 - 4(-3) = 25 + 12 = 37
x1 = (5 - √37)/2 ≈ -0,54
x2 = (5 + √37)/2 ≈ 5,54
2) x^2 - x - 4 = 0
D = 1^2 - 4(-4) = 1 + 16 = 17
x3 = (1 - √17)/2 ≈ -1,56
x4 = (1 + √17)/2 ≈ 2,56
3) x - 2 = 0
x5 = 2
Выпишем все промежутки в порядке возрастания:
(-oo; (1 - √17)/2); [(1 - √17)/2; (5 - √37)/2); [(5 - √37)/2; 2); [2; (1 + √17)/2);
[(1 + √17)/2; (5 + √37)/2); [(5 + √37)/2; +oo)
Теперь раскрываем модули.
1) x ∈ (-oo; (1 - √17)/2)
x^2 - 5x - 3 + x^2 - x - 4 = 5 + 2 - x
2x^2 - 6x - 7 - 7 + x = 0
2x^2 - 5x - 14 = 0
D = 5^2 - 4*2(-14) = 25 + 112 = 137
x1 = (5 - √137)/4 ≈ -1,676 ∈ (-oo; (1 - √17)/2) - РЕШЕНИЕ!
x2 = (5 + √137)/4 ≈ 4,176 ∉ (-oo; (1 - √17)/2) - не подходит
2) x ∈ [(1 - √17)/2; (5 - √37)/2)
x^2 - 5x - 3 + (-x^2 + x + 4) = 5 + 2 - x
-5x - 3 + x + 4 - 7 + x = 0
-3x - 10 = 0
x = -10/3 ≈ -3,333 ∉ [(1 - √17)/2; (5 - √37)/2) - не подходит
3) x ∈ [(5 - √37)/2; 2)
(-x^2 + 5x + 3) + (-x^2 + x + 4) = 5 + 2 - x
-2x^2 + 5x + 3 + x + 4 - 7 + x = 0
-2x^2 + 7x = 0
x1 = 0 ∈ [(5 - √37)/2; 2) - РЕШЕНИЕ!
x2 = 7/2 = 3,5 ∉ [(5 - √37)/2; 2) - не подходит
4) x ∈ [2; (1 + √17)/2)
(-x^2 + 5x + 3) + (-x^2 + x + 4) = 5 + x - 2
-2x^2 + 5x + 3 + x + 4 - 3 - x = 0
-2x^2 + 5x + 4 = 0
D = 5^2 - 4(-2)*4 = 25 + 32 = 57
x1 = (-5 - √57)/(-4) = (5 + √57)/4 ≈ 3,137 ∉ [2; (1 + √17)/2) - не подходит
x2 = (-5 + √57)/(-4) = (5 - √57)/4 ≈ -0,637 ∉ [2; (1 + √17)/2) - не подходит
5) x ∈ [(1 + √17)/2; (5 + √37)/2)
(-x^2 + 5x + 3) + x^2 - x - 4 = 5 + x - 2
5x + 3 - x - 4 - 3 - x = 0
3x - 4 = 0
x = 4/3 ≈ 1,333 ∉ [(1 + √17)/2; (5 + √37)/2) - не подходит
6) x ∈ [(5 + √37)/2; +oo)
x^2 - 5x - 3 + x^2 - x - 4 = 5 + x - 2
2x^2 - 6x - 7 - 3 - x = 0
2x^2 - 7x - 10 = 0
D = 7^2 - 4*2(-10) = 49 + 80 = 129
x1 = (7 - √129)/4 ≈ -1,089 ∉ [(5 + √37)/2; +oo) - не подходит
x2 = (7 + √129)/4 ≈ 4,589 ∉ [(5 + √37)/2; +oo) - не подходит
Ответ: x1 = (5 - √137)/4; x2 = 0
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Answers & Comments
|x^2 - 5x - 3| + |x^2 - x - 4| = 5 + |x - 2|
Сначала найдем корни в модулях:
1) x^2 - 5x - 3 = 0
D = 5^2 - 4(-3) = 25 + 12 = 37
x1 = (5 - √37)/2 ≈ -0,54
x2 = (5 + √37)/2 ≈ 5,54
2) x^2 - x - 4 = 0
D = 1^2 - 4(-4) = 1 + 16 = 17
x3 = (1 - √17)/2 ≈ -1,56
x4 = (1 + √17)/2 ≈ 2,56
3) x - 2 = 0
x5 = 2
Выпишем все промежутки в порядке возрастания:
(-oo; (1 - √17)/2); [(1 - √17)/2; (5 - √37)/2); [(5 - √37)/2; 2); [2; (1 + √17)/2);
[(1 + √17)/2; (5 + √37)/2); [(5 + √37)/2; +oo)
Теперь раскрываем модули.
1) x ∈ (-oo; (1 - √17)/2)
x^2 - 5x - 3 + x^2 - x - 4 = 5 + 2 - x
2x^2 - 6x - 7 - 7 + x = 0
2x^2 - 5x - 14 = 0
D = 5^2 - 4*2(-14) = 25 + 112 = 137
x1 = (5 - √137)/4 ≈ -1,676 ∈ (-oo; (1 - √17)/2) - РЕШЕНИЕ!
x2 = (5 + √137)/4 ≈ 4,176 ∉ (-oo; (1 - √17)/2) - не подходит
2) x ∈ [(1 - √17)/2; (5 - √37)/2)
x^2 - 5x - 3 + (-x^2 + x + 4) = 5 + 2 - x
-5x - 3 + x + 4 - 7 + x = 0
-3x - 10 = 0
x = -10/3 ≈ -3,333 ∉ [(1 - √17)/2; (5 - √37)/2) - не подходит
3) x ∈ [(5 - √37)/2; 2)
(-x^2 + 5x + 3) + (-x^2 + x + 4) = 5 + 2 - x
-2x^2 + 5x + 3 + x + 4 - 7 + x = 0
-2x^2 + 7x = 0
x1 = 0 ∈ [(5 - √37)/2; 2) - РЕШЕНИЕ!
x2 = 7/2 = 3,5 ∉ [(5 - √37)/2; 2) - не подходит
4) x ∈ [2; (1 + √17)/2)
(-x^2 + 5x + 3) + (-x^2 + x + 4) = 5 + x - 2
-2x^2 + 5x + 3 + x + 4 - 3 - x = 0
-2x^2 + 5x + 4 = 0
D = 5^2 - 4(-2)*4 = 25 + 32 = 57
x1 = (-5 - √57)/(-4) = (5 + √57)/4 ≈ 3,137 ∉ [2; (1 + √17)/2) - не подходит
x2 = (-5 + √57)/(-4) = (5 - √57)/4 ≈ -0,637 ∉ [2; (1 + √17)/2) - не подходит
5) x ∈ [(1 + √17)/2; (5 + √37)/2)
(-x^2 + 5x + 3) + x^2 - x - 4 = 5 + x - 2
5x + 3 - x - 4 - 3 - x = 0
3x - 4 = 0
x = 4/3 ≈ 1,333 ∉ [(1 + √17)/2; (5 + √37)/2) - не подходит
6) x ∈ [(5 + √37)/2; +oo)
x^2 - 5x - 3 + x^2 - x - 4 = 5 + x - 2
2x^2 - 6x - 7 - 3 - x = 0
2x^2 - 7x - 10 = 0
D = 7^2 - 4*2(-10) = 49 + 80 = 129
x1 = (7 - √129)/4 ≈ -1,089 ∉ [(5 + √37)/2; +oo) - не подходит
x2 = (7 + √129)/4 ≈ 4,589 ∉ [(5 + √37)/2; +oo) - не подходит
Ответ: x1 = (5 - √137)/4; x2 = 0