Question

giúp e với m.n ơiii

 

Answer 1

Bài 23:

\(2x^2-3x+1=0\)

=>\(2x^2-2x-x+1=0\)

=>(x-1)(2x-1)=0

=>x∈{1;1/2}

=>A={1;1/2}

\(\left(x^2-10x+21\right)\left(x^3-x\right)=0\)

=>\(x\left(x^2-1\right)\left(x-3\right)\left(x-7\right)=0\)

=>x(x-1)(x+1)(x-3)(x-7)=0

=>x∈{1;-1;0;3;7}

=>B={1;-1;0;3;7}

-3<2x+1<5

=>-4<2x<4

=>-2<x<2

mà x∈Z

nên x∈{-1;0;1}

=>C={-1;0;1}

X=A\(\cup\) B\(\cup\) C

={1;1/2}\(\cup\) {-1;1;0;3;7}\(\cup\) {-1;0;1}

={-1;1;0;3;7;1/2}

Bài 19:

Để \(\frac{2x-1}{x+3}\) là số nguyên thì 2x-1⋮x+3

=>2x+6-7⋮x+3

=>-7⋮x+3

=>x+3∈{1;-1;7;-7}

=>x∈{-2;-4;4;-10}

=>A={-2;-4;4;-10}

B={4;6;8;10}

A\(\cap\) B={-2;-4;4;-10}\(\cap\) {4;6;8;10}

={4}

A\(\cup\) B={-2;-4;4;-10}\(\cup\) {4;6;8;10}

={-2;-4;4;-10;6;8}