Question

Answer 1

\(E=\dfrac{5-3x}{4x-8}\)

\(=-\dfrac{3x-5}{4x-8}\)

\(=-\dfrac{1}{4}\cdot\dfrac{12x-20}{4x-8}\)

\(=-\dfrac{1}{4}\cdot\dfrac{12x-16-4}{4x-8}\)

\(=-\dfrac{1}{4}\left(3-\dfrac{4}{4x-8}\right)\)

\(=-\dfrac{1}{4}\left(3-\dfrac{1}{x-2}\right)\)

Để E min thì \(3-\dfrac{1}{x-2}\) max

=>\(\dfrac{1}{x-2}\) min

=>x-2=-1

=>x=1