`D=(a+4sqrta+4)/(sqrta+2)+(4-a)/(sqrta-2)`

`=(sqrta+2)^2/(sqrta+2)+((2-sqrta)(2+sqrta))/(sqrta-2)`

`=sqrta+2-(2+sqrta)`

`=0`

ĐK: a ≥ 0; a khác 4

\(D=\dfrac{a+\sqrt{a}+4}{\sqrt{a}+2}+\dfrac{\left(2-\sqrt{a}\right)\left(2+\sqrt{a}\right)}{\sqrt{a}-2}\)

\(=\dfrac{a+\sqrt{a}+4}{\sqrt{a}+2}-\left(2+\sqrt{a}\right)\)

\(=\dfrac{\left(a+\sqrt{a}+4\right)-\left(2+\sqrt{a}\right)^2}{\sqrt{a}+2}=\dfrac{a+\sqrt{a}+4-\left(4+4\sqrt{a}+a\right)}{\sqrt{a}+2}=\dfrac{a+\sqrt{a}+4-4-4\sqrt{a}-a}{\sqrt{a}+2}=-\dfrac{3}{\sqrt{a}}\)

576,(6)

13840 : 24 = 576,(6)

576,(6)

=1400

412 + 988

=1400

tính nhanh nha mn^^

12/7 x 14/3 = 168/21 = 8

\(=\dfrac{12}{7}\times\dfrac{14}{3}=8\)

\(\dfrac{12}{7}.\dfrac{14}{3}=\dfrac{168}{21}\)

\(\dfrac{24}{-4}\le x< \dfrac{-14}{7}\)

\(=\dfrac{-24}{4}\le x< \dfrac{-14}{7}\)

\(=-6\le x< -2\)

\(\Rightarrow\) x \(\in\) {-6;-5;-4;-3} 

Vậy chọn B

B

\(=\dfrac{\left(\sqrt{a}-1\right)\left(a+\sqrt{a}+1\right)}{\sqrt{a}\left(\sqrt{a}-1\right)}-\dfrac{\left(\sqrt{a}+1\right)\left(a-\sqrt{a}+1\right)}{\sqrt{a}\left(\sqrt{a}+1\right)}\)

\(=\dfrac{a+\sqrt{a}+1-a+\sqrt{a}-1}{\sqrt{a}}=\dfrac{2\sqrt{a}}{\sqrt{a}}=2\)

mẹ = 31

con = 7