\(B=\dfrac{1}{16}c^2-9c+10=\left(\dfrac{1}{16}c^2-9c+324\right)-314\)\(=\left(\dfrac{1}{4}c-18\right)^2-314\ge-314\)\(minB=-314\Leftrightarrow c=72\)Câu trả lời: \(B=\dfrac{1}{16}c^2-9c+10=\left(\dfrac{1}{16}c^2-9c+324\right)-314\)\(=\left(\dfrac{1}{4}c-18\right)^2-314\ge-314\)\(minB=-314\Leftrightarrow c=72\)