a: \(A=x^2-12x+36-6=\left(x-6\right)^2-6>=-6\)
Dấu '=' xảy ra khi x=6
b: \(B=16x^2+40x+25+6=\left(2x+5\right)^2+6>=6\)
Dấu '=' xảy ra khi x=-5/2
c: \(C=x^2-2\cdot x\cdot\dfrac{15}{2}+\dfrac{225}{4}+\dfrac{15}{4}=\left(x-\dfrac{15}{2}\right)^2+\dfrac{15}{4}>=\dfrac{15}{4}\)
Dấu '=' xảy ra khi x=15/2
d: \(D=x^2+2\cdot x\cdot\dfrac{17}{2}+\dfrac{289}{4}+\dfrac{11}{4}=\left(x+\dfrac{17}{2}\right)^2+\dfrac{11}{4}>=\dfrac{11}{4}\)
Dấu '=' xảy ra khi x=-17/2