17. coming 18. iron___ doing 19. wakes 20. buying

coming 

ỉon        doing 

wakes

buying

17. to come    18.iron , doing.  19.wake.  

Trl:

2 + 2 + 2 - 3 + 1

= 4 + 2 - 3 + 1

= 6 - 3 + 1

= 3 + 1

= 4

HT

= 4 hehehehehehehehehehehehehehehehehehehehhheheheheheehehe quá dễ

\(a,ĐKXĐ:\left\{{}\begin{matrix}8-4x\ge0\\5x-10\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\le2\\x\ne2\end{matrix}\right.\Leftrightarrow x< 2\\ b,ĐKXĐ:\left\{{}\begin{matrix}\dfrac{-3}{x+2}\ge0\\x^2+2\ge0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x+2< 0\left(-3< 0;x+2\ne0\right)\\x\in R\left(x^2+2\ge2>0\right)\end{matrix}\right.\Leftrightarrow x< -2\)

\(\Rightarrow\left[{}\begin{matrix}\dfrac{2}{3}-x=3\sqrt{3}\\\dfrac{2}{3}-x=-3\sqrt{3}\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{2-9\sqrt{3}}{3}\\x=\dfrac{2+9\sqrt{3}}{3}\end{matrix}\right.\)