a)
Ta có :
\(C=-x^2+5x\)
\(\Rightarrow C=-x^2+2.5x.\frac{1}{2}-\frac{1}{4}+\frac{1}{4}\)
\(\Rightarrow C=-\left(x^2-2.5x.\frac{1}{2}+\frac{1}{4}\right)+\frac{1}{4}\)
\(\Rightarrow C=-\left(x+\frac{1}{2}\right)^2+\frac{1}{4}\)
Ta có : \(\left(x+\frac{1}{2}\right)^2\ge0\)
\(\Rightarrow-\left(x+\frac{1}{2}\right)^2\le0\)
\(\Rightarrow-\left(x+\frac{1}{2}\right)^2+\frac{1}{4}\le\frac{1}{4}\)
Dấu " = " xảy ra khi \(x=-\frac{1}{2}\)
Vậy MAXC= 1 / 4 khi x = - 1 / 2
b)
Sai đề
Đúng 0
Bình luận (1)
mai phai nop bai rui moi nguoi jup em vs
Đúng 0
Bình luận (0)
