Let x = (x1, ... ,xn) and y = (y1,...,yn) ∈ Rn be fixed. Recall that Rn is a vector space, and that it is an inner product space when equipped with ⟨x,y⟩ = Σ nj=1 xnyn, where Σ is the summation notation.  This problem walks you through in proving the Cauchy-Schwartz inequality for this inner product. (a) For z ∈ R, Verify the following identity:P(z) = (x1z + y1)2 + (x2z + y2)2 + ··· + (xnz + yn)2          = (Σnj=1 x2j )z2 + 2 (Σnj=1? xjyj)z + Σnj=1 y2j. (b)  Explain why this polynomial P(z) is always nonnegative.

Linear Algebra: A Modern Introduction
4th Edition
ISBN:9781285463247
Author:David Poole
Publisher:David Poole
Chapter6: Vector Spaces
Section6.4: Linear Transformations
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Let x = (x1, ... ,xn) and y = (y1,...,yn) ∈ Rn be fixed. Recall that Rn is a vector space, and that it is an inner product space when equipped with

⟨x,y⟩ = Σ nj=1 xnyn, where Σ is the summation notation. 

This problem walks you through in proving the Cauchy-Schwartz inequality for this inner product.

(a) For z ∈ R, Verify the following identity:
P(z) = (x1z + y1)2 + (x2z + y2)2 + ··· + (xnz + yn)

        = (Σnj=1 x2j )z+ 2 (Σnj=1? xjyj)z + Σnj=1 y2j.

(b)  Explain why this polynomial P(z) is always nonnegative.

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