Question

Câu 4,10,11 nha

Answer 1

\(4,\\ a,=x^2+6x+9+2x-x^2=8x+9\\ b,=9x^2-12x+4-9x^2+1=5-12x\\ 11,\\ M=5\left(x^2-\dfrac{3}{5}x+\dfrac{2}{5}\right)\\ M=5\left(x^2-2\cdot\dfrac{3}{10}x+\dfrac{9}{100}+\dfrac{31}{100}\right)\\ M=5\left(x-\dfrac{3}{10}\right)^2+\dfrac{31}{20}\ge\dfrac{31}{20}\\ M_{min}=\dfrac{31}{20}\Leftrightarrow x=\dfrac{3}{10}\)