C
cloudymay


bai 1:
[TEX]\left\{ \begin{array}{l} \sqrt{x^2 + x + y + 1} + x + sqrt{x^2 + x + y + 1} + y = 18 \\ sqrt{x^2 + x + y + 1} - x + sqrt{x^2 + x + y + 1} - y = 2 \end{array} \right. [/TEX]
bai 2:
[TEX](4x - 1)sqrt{x^2 + 2x - 1} = 2{x^2} + 2x + 1[/TEX]
[TEX]\left\{ \begin{array}{l} \sqrt{x^2 + x + y + 1} + x + sqrt{x^2 + x + y + 1} + y = 18 \\ sqrt{x^2 + x + y + 1} - x + sqrt{x^2 + x + y + 1} - y = 2 \end{array} \right. [/TEX]
bai 2:
[TEX](4x - 1)sqrt{x^2 + 2x - 1} = 2{x^2} + 2x + 1[/TEX]