(2) Let R = Z[√5] and R* = R−0. Consider the nomm map N : R* → Z*. If a, b = Z, we set N(a+b√-5) = (a+b√−5)(a − b√−5) = a² + 5b². Show that if x, y = R*, then N(xy) = N(x)N(y). (b) Show that u € R* is a unit if and only N(u) is a unit in Z. (c) Let U(R) be the set of units in R. Show that U(R) = {−1, +1}.
(2) Let R = Z[√5] and R* = R−0. Consider the nomm map N : R* → Z*. If a, b = Z, we set N(a+b√-5) = (a+b√−5)(a − b√−5) = a² + 5b². Show that if x, y = R*, then N(xy) = N(x)N(y). (b) Show that u € R* is a unit if and only N(u) is a unit in Z. (c) Let U(R) be the set of units in R. Show that U(R) = {−1, +1}.
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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