View attachment 104596
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[tex] \left ( 2 \right )[/tex] :[tex]x^{2}+9= y^{2}+2y-4 \left (dk: y \leq 5\right )[/tex] [tex]\Leftrightarrow x^{2}+4= y^{2}-10y+20[/tex][tex]\left ( \ast \right )[/tex]
Thế [tex]\left ( \ast \right )[/tex] vào [tex]\left ( 1 \right )[/tex] ,ta có :
[tex] \sqrt{y^{2}-10y+20}+\sqrt{y^{2}+2y-4}= 4[/tex]
[tex] \Leftrightarrow \left ( \sqrt{y^{2}-10y+20}-y \right )+\left ( \sqrt{y^{2}+2y-4} -y\right )+2\left ( y-2 \right )= 0[/tex]
[tex] \Leftrightarrow \frac{-10y+20}{\sqrt{y^{2}-10y+20}+y}+\frac{2y-4}{\sqrt{y^{2}+2y-4}+y}+2\left ( y-2 \right )= 0[/tex]
[tex] \Leftrightarrow \left ( y-2 \right )\left ( \frac{-5}{\sqrt{y^{2}-10y+20}+y} +\frac{2}{\sqrt{y^{2}+2y-4}+y}+2\right )= 0[/tex]
Do [tex] y\leq 5[/tex] suy ra cụm lớn đằng sau khác 0 ....
[TẶNG BẠN] TRỌN BỘ Bí kíp học tốt 08 môn
