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Answers for “如何将向量乘以标量?”

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The mathematician generalizes the concept to any object that supports sensible addition and scalar multiplication operations.

Conditions: Abstract linear algebra context

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Scalar multiplication preserves the relation because multiplying the equation x3=x1+x2x_3 = x_1 + x_2 by a scalar cc yields cx3=cx1+cx2cx_3 = cx_1 + cx_2. This shows that the third component of the scaled vector cxcx equals the sum of its first and second components.

Conditions: xx is a vector in the set satisfying x3=x1+x2x_3 = x_1 + x_2.; cc is a real scalar.; Scalar multiplication is defined componentwise.

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The length is multiplied by the absolute value of the scalar ∣c∣|c|. Specifically, 0<∣c∣<10 < |c| < 1 shortens the vector, ∣c∣>1|c| > 1 stretches it, and c=0c=0 yields the zero vector.

Conditions: Scalar multiplication operation; Considering magnitude/length changes

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To add vectors, you add their corresponding components. This means if you have two vectors, you sum the first component of each to get the first component of the result, and similarly for the second component.

Conditions: The vectors must have the same dimension (e.g., both are 2D or both are 3D).; The components are aligned by position (first with first, second with second).

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Multiplying a 3x3 matrix by a vector (x,y,z)(x, y, z) scales each column of the matrix (which represents a transformed basis vector) by the corresponding input coordinate and sums the results. This works because linear transformations preserve addition and scalar multiplication.

Conditions: Matrix is 3x3 representing a linear transformation; Input vector has coordinates (x,y,z)(x, y, z); Transformation is linear

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The set is considered a subspace because vectors of the form (x,0,−x) stay in the same form after addition or scalar multiplication. This set is the span of (1,0,−1), a line through the origin.

Conditions: The vectors are of the form (x,0,-x).; The operation is vector addition or scalar multiplication.

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A linear combination of two arbitrary non-collinear vectors v⃗\vec{v} and w⃗\vec{w} is formed by multiplying each vector by a scalar (aa and bb) and adding them together (av⃗+bw⃗a\vec{v} + b\vec{w}). If both scalars are allowed to vary continuously across all real numbers, the tips of these combined vectors sweep out every possible point on the 2D plane.

Conditions: The two vectors v⃗\vec{v} and w⃗\vec{w} are non-collinear (point in different directions and do not lie on the same line).; The scalars aa and bb vary continuously across all real numbers.

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First, calculate the dot products y⋅u=20y \cdot u = 20 and u⋅u=5u \cdot u = 5. The scalar coefficient is 20/5=420/5 = 4.

Conditions: y=(7,6)y = (7,6); u=(2,1)u = (2,1)

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Subtraction is equivalent to adding the additive inverse. In matrix algebra, multiplying a matrix by the scalar -1 creates its additive inverse.

Conditions: Scalar multiplication by -1 is defined entrywise.; Matrix addition is defined entrywise.; A and B have the same dimensions.