Question

Câu 1: Tìm x:

\(\left(x-3\right)^2=16\)

Câu 2: a) Tìm \(x\in Z\) biết: \(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{2}{5}\le x< 4\dfrac{1}{5}+3\dfrac{1}{2}\)

b) So sánh: \(\dfrac{-12}{21}\) và \(\dfrac{10}{-28}\)

(Ai làm trước mình tick cho)

Answer 1

Câu 1:

\(\left(x-3\right)^2=16\)

\(\Rightarrow\)\(\left[{}\begin{matrix}x-3=4\\x-3=-4\end{matrix}\right.\)

\(\Rightarrow\)\(\left[{}\begin{matrix}x=7\\x=-1\end{matrix}\right.\)

vậy x\(\in\)\(\left\{7;-1\right\}\)

câu2:a,

\(\Rightarrow\)\(\dfrac{13}{30}\le x< \dfrac{77}{10}\)

mà x\(\in\)Z\(\Rightarrow\)x\(\in\)\(\left\{1;2;3;4;5;6\right\}\)

vậy x\(\in\)\(\left\{1;2;3;4;5;6\right\}\)

b, ta có: \(\dfrac{-12}{21}=\dfrac{-48}{84}\);\(\dfrac{10}{-28}=\dfrac{-10}{28}=\dfrac{-30}{84}\)

mà \(\dfrac{-48}{84}< \dfrac{-30}{84}\)\(\Rightarrow\)\(\dfrac{-12}{21}< \dfrac{10}{-28}\)