- một phần hai mét

- ba phần mười đề xi mét

- ba phần bốn kí lô gam

- ba phần hai lít

- sáu phần năm ki lô mét

- sáu mươi bảy phần tám mươi bốn gam

1. thay x = 25 vào A ta được:

\(A=\frac{\sqrt{25}-3}{\sqrt{25}-1}=\frac{5-3}{5-1}=\frac24=\frac12\)

2. \(B=\left(\frac{x+\sqrt{x}-5}{x-4}-\frac{3}{\sqrt{x}+2}\right):\frac{\sqrt{x}-1}{\sqrt{x}-2}\)

\(=\left\lbrack\frac{x+\sqrt{x}-5}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}-\frac{3\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\right\rbrack\cdot\frac{\sqrt{x}-2}{\sqrt{x}-1}\)

\(=\frac{x+\sqrt{x}-5-3\sqrt{x}+6}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\cdot\frac{\sqrt{x}-2}{\sqrt{x}-1}\)

\(=\frac{x-2\sqrt{x}+1}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\cdot\frac{\sqrt{x}-2}{\sqrt{x}-1}\)

\(=\frac{\left(\sqrt{x}-1\right)^2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\cdot\frac{\sqrt{x}-2}{\sqrt{x}-1}\)

\(=\frac{\sqrt{x}-1}{\sqrt{x}+2}\)

3. \(P=A\cdot B=\frac{\sqrt{x}-3}{\sqrt{x}-1}\cdot\frac{\sqrt{x}-1}{\sqrt{x}+2}\)

\(=\frac{\sqrt{x}-3}{\sqrt{x}+2}=\frac{\sqrt{x}+2-5}{\sqrt{x}+2}=1-\frac{5}{\sqrt{x}+2}\)

\(\) để \(1-\frac{5}{\sqrt{x}+2}\) đạt GTNN thì \(\frac{5}{\sqrt{x}+2}\) đạt GTLN

\(\frac{5}{\sqrt{x}+2}\) đạt GTLN khi \(\sqrt{x}+2\) đạt GTNN

điều này xảy ra khi x =0

khi đó GTNN của biểu thức là: \(1-\frac52=-\frac32\)

67-67=0

bác sinh 19 tháng 5, 1890

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20

= 20 x (20 + 1) : 2 = 210

\(\frac45;\frac54;\frac34;\frac{56}{57}\)

diện tích hình tam giác là:

21 x 42 : 2 = 441 (m2)

\(P=\left(\frac{2x\sqrt{x}+x-\sqrt{x}}{x\sqrt{x}-1}-\frac{x+\sqrt{x}}{x-1}\right)\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(2x\sqrt{x}+x-\sqrt{x}\right)\left(\sqrt{x}+1\right)-\left(x+\sqrt{x}\right)\left(x+\sqrt{x}+1\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{2x^2+3x\sqrt{x}-\sqrt{x}-x^2-2x\sqrt{x}-2x-\sqrt{x}}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{x^2+x\sqrt{x}-2x-2\sqrt{x}}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(x-2\right)\left(x+\sqrt{x}\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(x-2\right)\left(\sqrt{x}+1\right)\cdot\sqrt{x}}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(x-2\right)\cdot\sqrt{x}}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{x-1}{2x+\sqrt{x}-1}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(x-2\right)\cdot\sqrt{x}}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\cdot\frac{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}{\left(2\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\sqrt{x}\left(x-2\right)}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}+\frac{\sqrt{x}}{2\sqrt{x}-1}\)

\(=\frac{\left(x-2\right)\sqrt{x}+\sqrt{x}\left(x+\sqrt{x}+1\right)}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\)

\(=\frac{x\sqrt{x}-2\sqrt{x}+x\sqrt{x}+x+\sqrt{x}}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\)

\(=\frac{2x\sqrt{x}+x-\sqrt{x}}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\)

\(=\frac{\sqrt{x}\left(2x+\sqrt{x}-1\right)}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\)

\(=\frac{\sqrt{x}\left(2\sqrt{x}-1\right)\left(\sqrt{x}+1\right)}{\left(2\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\)

\(=\frac{\sqrt{x}\left(\sqrt{x}+1\right)}{x+\sqrt{x}+1}\)

B

11: Eleven

12: Twelve

13: Thirteen

14: Fourteen

15: Fifteen

16: Sixteen

17: Seventeen

18: Eighteen

19: Nineteen

20: Twenty