Question

tìm xy thuộc N biết                                                                                                               a, 3x+5 . 2x+1 

b, 4xy+3x+2y =16

Answer 1

a: 3x+5 chia hêt cho 2x+1

=>6x+10 chia hết cho 2x+1

=>6x+3+7 chia hết cho 2x+1

=>\(2x+1\in\left\{1;7\right\}\)

=>x=0; x=3

b: 4xy+3x+2y=16

=>2y(2x+1)+3x+1,5=17,5

=>(2x+1)(2y+1,5)=17,5

=>(4y+3)(2x+1)=35

=>\(\left(2x+1;4y+3\right)\in\left\{\left(1;35\right);\left(35;1\right);\left(5;7\right);\left(7;5\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(0;8\right);\left(2;1\right)\right\}\)