a) Q=13-(x^2+4x+4)=13-(x+2)^2<=13 Qmax=13 khi x=-2
b) M=\(6x-x^2+74+x=74-\left(x^2+7x\right)=74-\left(x^2-2.\frac{7}{2}x+\left(\frac{7}{2}\right)^2\right)^{^2}-\left(\frac{7}{2}\right)^2\\ \)
\(\frac{74\cdot4-49}{4}-\left(x-\frac{7}{2}\right)^2\le\frac{74\cdot4-49}{4}=M_{max}\)đảng thức khi x=7/2
C) \(P=\frac{25}{4}-\left(x^2-2.\frac{5}{2}+\left(\frac{5}{2}\right)^2\right)=\frac{25}{4}-\left(x-\frac{5}{2}\right)^2\le\frac{25}{4}=P_{max}\) khi x=5/2
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