Biến đổi:

B : A = <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><mrow><mn>2</mn><msqrt><mi>x</mi></msqrt></mrow><mrow><msqrt><mi>x</mi></msqrt><mo>-</mo><mn>2</mn></mrow></mfrac><mo>&#xF7;</mo><mfrac><mrow><msqrt><mi>x</mi></msqrt><mo>&#xA0;</mo><mo>+</mo><mn>1</mn></mrow><mrow><msqrt><mi>x</mi></msqrt><mo>&#xA0;</mo><mo>-</mo><mn>2</mn></mrow></mfrac><mo>=</mo><mo>&#xA0;</mo><mfrac><mrow><mn>2</mn><msqrt><mi>x</mi></msqrt></mrow><mrow><msqrt><mi>x</mi></msqrt><mo>-</mo><mn>2</mn></mrow></mfrac><mo>&#xD7;</mo><mfrac><mrow><msqrt><mi>x</mi></msqrt><mo>&#xA0;</mo><mo>-</mo><mn>2</mn></mrow><mrow><msqrt><mi>x</mi></msqrt><mo>&#xA0;</mo><mo>+</mo><mn>1</mn></mrow></mfrac><mo>=</mo><mfrac><mrow><mn>2</mn><msqrt><mi>x</mi></msqrt></mrow><mrow><msqrt><mi>x</mi></msqrt><mo>+</mo><mn>1</mn></mrow></mfrac></math>

Rồi giải tiếp như mình gửi ảnh nha.

$\frac{2\sqrt{x}}{\sqrt{x}-2}÷\frac{\sqrt{x}+1}{\sqrt{x}-2}= \frac{2\sqrt{x}}{\sqrt{x}-2}\times \frac{\sqrt{x}-2}{\sqrt{x}+1}=\frac{2\sqrt{x}}{\sqrt{x}+1}$

nãy mình type lỗi sr bạn nha