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

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

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

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

Vậy chọn B

B

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

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

\(1,=10\sqrt{2}-21\sqrt{2}+3\sqrt{2}=-8\sqrt{2}\\ 2,=\dfrac{6\left(\sqrt{5}+1\right)}{4}=\dfrac{3\sqrt{5}+3}{2}\\ 3,=2+\left|2-\sqrt{7}\right|=2+\sqrt{7}-2=\sqrt{7}\)

\(-\dfrac{2}{5}\times\left(-\dfrac{1}{2}\right)\times\left(-\dfrac{4}{5}\right)=-\dfrac{4}{25}=-0.16\)

= -0,16

3.

\(F=\dfrac{k.\left|q_1.q_2\right|}{r^2}=\dfrac{9.10^9.\left|9.10^{-18}\right|}{0,1^2}=8,1.10^{-6}N\)

2. C

1.

\(F=\dfrac{k.\left|q_1.q_2\right|}{r^2}=\dfrac{9.10^9.\left|5.10^8.\left(-1,6.10^{-19}\right).5.10^8.\left(-1,6.10^{-19}\right)\right|}{0,02^2}=1,44.10^{-7}N\)

ý c đúng nha bn

C

do \(\dfrac{123}{124}=\dfrac{15375}{15500}\)

\(\dfrac{124}{125}=\dfrac{15376}{15500}\)

mà 15375<15376

vậy \(\dfrac{123}{124}< \dfrac{124}{125}\)