Question

Tìm GTNN của 𝐶 = 3^2 - x + 5

Answer 1

Sửa: `C=3x^2-x+5`

`<=>C=3(x^2-1/3x+5/3)`

`<=>C=3(x^2-2x . 1/6+1/36+59/36)`

`<=>C=3(x-1/6)^2+59/12`

 Vì `3(x-1/6)^2 >= 0 AA x<=>3(x-1/6)^2+59/12 >= 59/12 AA x`

              Hay `C >= 59/12 AA x`

Dấu "`=`" xảy ra `<=>x-1/6=0<=>x=1/6`