(a) Prove that if A and B are nonempty, bounded sets of real numbers such that x ≤ y for all x € A and y € B, then we have sup(A) ≤ inf(B). (b) Deduce from this result the "middle inequality" of Lemma 7.8.

Advanced Engineering Mathematics
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Chapter2: Second-order Linear Odes
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(a) Prove that if A and B are nonempty, bounded sets of real numbers such that x ≤ y for all x € A
and y E B, then we have sup(A) ≤ inf(B).
(b) Deduce from this result the "middle inequality" of Lemma 7.8.
Transcribed Image Text:(a) Prove that if A and B are nonempty, bounded sets of real numbers such that x ≤ y for all x € A and y E B, then we have sup(A) ≤ inf(B). (b) Deduce from this result the "middle inequality" of Lemma 7.8.
The lower integral of f is defined to be
L(f) = sup{L(f, P) : P = P}.
LEMMA 7.8. Let f: [a, b] → R be a bounded function, say, m ≤ f(x) ≤ M for all x € [a, b]. Then
we have
m(b − a) ≤ L(f) ≤ U(f) ≤ M(b − a).
Transcribed Image Text:The lower integral of f is defined to be L(f) = sup{L(f, P) : P = P}. LEMMA 7.8. Let f: [a, b] → R be a bounded function, say, m ≤ f(x) ≤ M for all x € [a, b]. Then we have m(b − a) ≤ L(f) ≤ U(f) ≤ M(b − a).
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