Linear combinations

Created almost 9 years ago, updated 6 months ago

Definition: A linear combination of vectors \(\mathbf{v}_1, \mathbf{v}_2, \ldots, \mathbf{v}_k\) in a vector space \(V\) is any vector of the form:
\[c_1\mathbf{v}_1 + c_2\mathbf{v}_2 + \cdots + c_k\mathbf{v}_k\]
where \(c_1, c_2, \ldots, c_k\) are scalars (from the underlying field).

The scalars \(c_i\) are called the coefficients of the linear combination.

Example: In \(\mathbb{R}^3\), the vector \((7, 4, -3)\) is a linear combination of the standard basis vectors:
\[(7, 4, -3) = 7(1,0,0) + 4(0,1,0) + (-3)(0,0,1)\]

Example: The vector \((5, 8)\) is a linear combination of \((1, 2)\) and \((3, 4)\) because:
\[(5, 8) = 1 \cdot (1, 2) + 2 \cdot (3, 4)\]

Linear combinations are the fundamental operation in linear algebra; they describe how vectors can be built from others using only addition and scalar multiplication.

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