Question

Bài 1 : Tính hợp lí

A=48+(-48-174)+\(|-74|\)

B=(-123)+77+(-257)-23-43

C=(-57)+(-159)+47+169

D=(135-35).(-47)+53.(-48-52)

Bài 2: tìm \(x\in\)Z biết

a)2(x+1)=0

b)x(x-2)=0

c) (x-1)(x+7)=0

d) (x+2)(x² -9)=0

e) x² (x-5)+2(x-5)=0

Bài 3 : tìm x,y \(\in\)Z biết

(x-3)(y+2)=7

Answer 1

bài 2) a) \(2\left(x+1\right)=0\Leftrightarrow x+1=0\Leftrightarrow x=-1\) vậy \(x=-1\)

b) \(x\left(x-2\right)=0\Leftrightarrow\left\{{}\begin{matrix}x=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0\\x=2\end{matrix}\right.\) vậy \(x=0;x=2\)

c) \(\left(x-1\right)\left(x+7\right)=0\Leftrightarrow\left\{{}\begin{matrix}x-1=0\\x+7=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\x=-7\end{matrix}\right.\) vậy \(x=1;x=-7\)

d) \(\left(x+2\right)\left(x^2-9\right)=0\Leftrightarrow\left\{{}\begin{matrix}x+2=0\\x^2-9=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-2\\x^2=9\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-2\\\left\{{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\end{matrix}\right.\) vậy \(x=-2;x=3;x=-3\)

e) \(x^2\left(x-5\right)+2\left(x-5\right)=0\Leftrightarrow\left(x^2+2\right)\left(x-5\right)=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}x^2+2=0\\x-5=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x\in\varnothing\\x=5\end{matrix}\right.\) vậy \(x=5\)

Answer 2

bài 1) \(A=48+\left(-48-174\right)+\left|-74\right|=48-48-174+74=-100\)

\(B=\left(-123\right)+77+\left(-257\right)-23-43=-123+77-257-23-43=-369\)

\(C=\left(-57\right)+\left(-159\right)+47+169=-57-159+47+169=0\)

quá hợp lí