Maths Determinants
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New answer posted
3 weeks agoContributor-Level 10
| 1+x² |
| x 1+x | = − (x - α? ) (x − α? ) (x – α? ) (x – α? )
| x² x 1+x |
Put x = 0
| 1 0 |
| 0 1 0 | = - (-α? ) (-α? ) (-α? ) (-α? )
| 0 1 |
α ⇒? α? α? α? = −1
New answer posted
3 weeks agoContributor-Level 10
|adj (adj (A)| = |A|? ¹² = |A|?
|A| = | (14, 28, -14), (-14, 28), (25, -14, 14) |
= (14)² | (1, 2, -1), (-1, 2), (25/14, -1, 1) |
= (14)² (3–2 (–5)–1 (–1)
|A|? = (14)? => |A| = 14²
New answer posted
a month agoContributor-Level 9
(P? ¹AP - I)²
= (P? ¹AP - I) (P? ¹AP - I)
= P? ¹A (PP? ¹)AP - P? ¹AP - P? ¹AP + I
= P? ¹A²P - 2P? ¹AP + I
= P? ¹ (A² - 2A + I)P = P? ¹ (A - I)²P
| (P? ¹AP - I)²| = |P? ¹ (A - I)²P| = |P? ¹| | (A - I)²| |P| = | (A - I)²| = |A - I|²
A - I = [1, 7, w²], [-1, w², 1], [0, -w, -w]
|A - I| = 1 (-w³ + w) - 7 (w) + w² (w) = -w³ + w - 7w + w³ = -6w.
|A - I|² = (-6w)² = 36w².
New answer posted
a month agoContributor-Level 10
The problem involves a function f (x) defined by a determinant:
f (x) = | sin²x 1+cos²x cos2x |
| 1+sin²x cos²x cos2x |
| sin²x cos²x sin2x |
Applying the row operation R? → R? - R? , we get:
f (x) = | -1 0 |
| 1+sin²x cos²x cos2x |
| sin²x cos²x sin2x |
Expanding the determinant along the first row:
f (x) = -1 (cos²x * sin2x - cos2x * cos²x) - 1 (1+sin²x)sin2x - sin²x * cos2x)
= -cos²x * sin2x + cos2x * cos²x - sin2x - sin²x * sin2x + sin²x * cos2x
= -sin2x (cos²x + sin²x) + cos2x (cos²x + sin²x) - sin2x
= -sin2x + cos2x - sin2x
= cos2x - 2sin2x
To find the maximum value of f (x), we use the form acosθ + bsinθ, where the m
New answer posted
a month agoContributor-Level 10
For a system of linear homogeneous equations to have a non-trivial solution, the determinant of the coefficient matrix must be zero.
Δ = | 4 λ 2 |
| 2 -1 | = 0
| μ 2 3 |
To simplify, perform the row operation R? → R? - 2R? :
Δ = | 0 λ+2 0 |
| 2 -1 | = 0
| μ 2 3 |
Expand the determinant along the first row:
- (λ+2) * det (| 2 1 |, | μ 3 |) = 0.
- (λ+2) (2*3 - 1*μ) = 0.
(λ+2) (μ-6) = 0.
This implies that either λ+2 = 0 or μ-6 = 0.
So, the conditions are λ = -2 (for any μ) or μ = 6 (for any λ).
New answer posted
a month agoContributor-Level 10
We need to evaluate the sum:
Σ (100 - r) (100 + r) for r from 0 to 99.
Σ (100² - r²) for r from 0 to 99
= Σ 100² - Σ r² for r from 0 to 99
= 100 * 100² - [99 (99+1) (2*99+1)]/6
= 100³ - [99 * 100 * 199]/6
= 100³ - (1650 * 199)
Comparing this with (100)³ – 199β, we get:
β = 1650
If we consider a comparison form α = 3β, this part of the solution seems to have a typo, but based on the final calculation, Slope = α/β = 1650 / 3 = 550 seems to be intended.
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