Question

Tìm GTNN

A=x^-4x+1

B=\(\dfrac{-4}{x^2+4x-10}\)

C=\(\dfrac{-2}{x^2-x+1}\)

D=\(\dfrac{-6}{x^2-6x+12}\)

E=\(\dfrac{x}{x^2+4}\)

Answer 1

a: \(A=x^2-4x+4-3=\left(x-2\right)^2-3>=-3\)

Dấu = xảy ra khi x=2

b: \(x^2+4x-10=x^2+4x+4-14=\left(x+2\right)^2-14>=-14\)

\(\Leftrightarrow\dfrac{4}{x^2+4x-10}< =-\dfrac{4}{14}\)

=>B>=2/7

Dấu = xảy ra khi x=-2

c: \(x^2-x+1=\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}>=\dfrac{3}{4}\)

=>2/x^2-x+1<=2:3/4=8/3

=>C>=-8/3

Dấu = xảy ra khi x=1/2

d: x^2-6x+12=(x-3)^2+3>=3

=>6/x^2-6x+12<=2

=>D>=-2

Dấu = xảy ra khi x=3