Question

[Tran Thuy Trang]

Tìm x biết :

a)2|x-1|-|1-x|=12

b)1+5+9+13+...+x=5050

Giúp mk nhé!Cảm ơn các bạn nhiều!^^^!!!!

Answer 1

[Sakuraba Laura]

b)

\(1+5+9+13+...+x=5050\)           

\(\Rightarrow1+\left(2+3\right)+\left(4+5\right)+\left(6+7\right)+...+\left(a+a+1\right)=5050\)

                             Có a+1 số hạng

\(\Rightarrow\left(a+1+1\right)\left(a+1\right)\div2=5050\)

\(\Rightarrow\left(a+2\right)\left(a+1\right)\div2=5050\)

\(\Rightarrow\left(a+2\right)\left(a+1\right)=5050.2\)

\(\Rightarrow\left(a+2\right)\left(a+1\right)=10100\)

\(\Rightarrow\left(a+2\right)\left(a+1\right)=101.100\)

\(\Rightarrow a+1=100\)

\(\Rightarrow a=99\)

\(\Rightarrow x=99+100\)

\(\Rightarrow x=199\)

Vậy \(x=199\)

Answer 2

[Nguyễn Đình Toàn]

a) x = 13 hoặc x = -11 . 

b) x = 199 .