\(a.x^2-4x+4+y^2+2y+1\)

\(=\left(x-2\right)^2+\left(y+1\right)^2\)

12+21=33

7,1 +(-5,25) -(-2,25 +7,1)

= 7,1 -5,25 +  2,25 - 7,1

= -3

\(P=\frac{1}{\sqrt{1}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{5}}+......+\frac{1}{\sqrt{23}+\sqrt{25}}=\frac{\sqrt{3}-\sqrt{1}}{\left(1+\sqrt{3}\right)\left(\sqrt{3}-1\right)}+\frac{\sqrt{5}-\sqrt{3}}{\left(\sqrt{3}+\sqrt{5}\right)\left(\sqrt{5}-\sqrt{3}\right)}+.......+\frac{\sqrt{25}-\sqrt{23}}{\left(\sqrt{23}+\sqrt{25}\right)\left(\sqrt{25}-\sqrt{23}\right)}=\frac{\sqrt{3}-\sqrt{1}}{2}+\frac{\sqrt{5}-\sqrt{3}}{2}+......+\frac{\sqrt{25}-\sqrt{23}}{2}=\frac{\left(\sqrt{25}-\sqrt{23}\right)+\left(\sqrt{23}-\sqrt{21}\right)+......+\left(\sqrt{3}-1\right)}{2}\) \(=\frac{\sqrt{25}-1}{2}=\frac{5-1}{2}=\frac{4}{2}=2\)

hoa quỳnh

16 ngày nha bn