Question

Tìm số tự nhiên x :

a, 15 chia hết cho (2x + 1)

b, x+16 chia hết cho x+1

Answer 1

a) Ta có : \(\frac{15}{2x+1}\Rightarrow2x+1\inƯ\left(15\right)\Rightarrow2x+1\in\left\{1;3;5;15\right\}\Rightarrow x\in\left\{0;1;2;7\right\}\)

b) Ta có: \(\frac{x+16}{x+1}=\frac{x+1+15}{x+1}=1+\frac{15}{x+1}\Rightarrow x+1\inƯ\left(15\right)\Rightarrow x+1\in\left\{1;3;5;15\right\}\Rightarrow x\in\left\{0;2;4;14\right\}\)

Answer 2

  Ta có :a, 15 chia hết cho (2x + 1)

=> 2x + 1 thuộc Ư(15)

=> Ư(15) = {1;3;5;15}

=> 2x + 1 = {1;3;5;15}

=> 2x = {0;2;4;14}

=> x = {0;1;2;7}

b, x+16 chia hết cho x+1