B
bboy114crew
1.dk: x \geq -1
[TEX]pt \Leftrightarrow (\sqrt{x^2+x}-1)^2+2(x^2+x-1)=0[/TEX]
[TEX]\Leftrightarrow (\sqrt{x^2+x}-1)(3\sqrt{x^2+x}+1)=0[/TEX]
[TEX]\Rightarrow ...[/TEX]
6.[TEX]Dat: \ \left{\sqrt{1+x}=a \geq 0 \\ \sqrt{1-x}=b \geq 0[/TEX]
[TEX]hpt \Leftrightarrow \left{a^2+b^2=2\\ a+a^2+2=b+3ab[/TEX]
1)[tex]\sqrt {x + 1 + \sqrt {x + \frac{3}{4}} } = \frac{7}{4} [/tex]
[tex] \Leftrightarrow \sqrt {\left( {x + \frac{3}{4}} \right) + \sqrt {x + \frac{3}{4}} + \frac{1}{4}} = \frac{7}{4} [/tex]
[tex] \Leftrightarrow \sqrt {x + \frac{3}{4}} + \frac{1}{2} = \frac{7}{4} [/tex]
[tex] \Leftrightarrow x = \frac{{13}}{{16}} [/tex]
6) đặt [tex]\sqrt{x+1}=a , \sqrt{1-x} =b [/tex] pt trở thành [tex]2 a^{2} + b^{2} +a-b-3ab=0[/tex] suy ra (a-b)(2a-b+1)=0 kết hợp vs cả dk [tex] a^{2}+ b^{2}=2[/tex] để giải ra x
nói chung là giống bạn!