Yesterday once more; baby; call me baby; just give me a reason; everytime we touch; faded; until you; why not me; what are word; cry on my shoulder; It's not goodbye ; ..............................

Mk chỉ lm 1 bài còn lại cứ tương tự mà lm! Bn hx lớp 7 ak?

3) Ta có: x² + 2x + 2 = (x² + 2x +1 ) +1 = ( x+ 1)² +1

Vì ( x+ 1)² \(\ge\) 0 => ( x + 1)² + 1 \(\ge\) 1 > 0 (đpcm)

PTHH: 2NaOH + CO₂ --> Na₂CO₃ + H₂O

Ta có: \(n_{CO_2}\) = \(\dfrac{4,48}{22,4}\) = 0,2 mol

n_NaOH = \(\dfrac{16}{40}\) = 0,4 mol

=> \(m_{Na_2CO_3}\) = 0,2 x 106 = 21,2 g

b) Lm tương tự

c) \(C=x^2-4xy+5y^2+10x-22y+28\)

=> C = \(\left(x^2+4y^2+25-4xy-20y+10x\right)+\left(y^2-2y+1\right)+2\)

=> C = \(\left(x-2y+5\right)^2+\left(y-1\right)^2+2\)

Vì \(\left\{{}\begin{matrix}\left(x-2y+5\right)^2\ge0\\\left(y+1\right)^2\ge0\end{matrix}\right.\) => C \(\ge\) 2

=> Dấu bằng xảy ra <=> \(\left\{{}\begin{matrix}x-2y+5=0\\y-1=0\end{matrix}\right.\) <=> \(\left\{{}\begin{matrix}x=-3\\y=1\end{matrix}\right.\)

Vậy GTNN của C =2 khi x = -3; y= 1

1) A = x² - 6x + 11 = ( x² - 6x + 9 ) + 2 = (x - 3)² +2

Vì (x - 3 )² \(\ge\) 0 => ( x - 3)² + 2 \(\ge\) 2

=> Dấu = xảy ra <=> x = 3

Vậy .......................