P = x+2/x√x-1 – √x+1/x+√x+1 + 1/1-√x
a. Rút gọn P
b, Tìm P khi x = 33 – 8√2
P = x+2/x√x-1 – √x+1/x+√x+1 + 1/1-√x a. Rút gọn P b, Tìm P khi x = 33 – 8√2
By Camila
By Camila
P = x+2/x√x-1 – √x+1/x+√x+1 + 1/1-√x
a. Rút gọn P
b, Tìm P khi x = 33 – 8√2
Đáp án:
a. \(\dfrac{{ – \sqrt x – 2}}{{x + \sqrt x + 1}}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.DK:x \ge 0;x \ne 1\\
P = \dfrac{{x + 2 – \left( {\sqrt x + 1} \right)\left( {\sqrt x – 1} \right) – \left( {x + \sqrt x + 1} \right)}}{{\left( {\sqrt x – 1} \right)\left( {x + \sqrt x + 1} \right)}}\\
= \dfrac{{x + 2 – x + 1 – x – \sqrt x – 1}}{{\left( {\sqrt x – 1} \right)\left( {x + \sqrt x + 1} \right)}}\\
= \dfrac{{ – x – \sqrt x + 2}}{{\left( {\sqrt x – 1} \right)\left( {x + \sqrt x + 1} \right)}}\\
= \dfrac{{\left( {1 – \sqrt x } \right)\left( {\sqrt x + 2} \right)}}{{\left( {\sqrt x – 1} \right)\left( {x + \sqrt x + 1} \right)}}\\
= \dfrac{{ – \sqrt x – 2}}{{x + \sqrt x + 1}}\\
b.Thay:x = 33 – 8\sqrt 2 \\
\to P = \dfrac{{ – \sqrt {33 – 8\sqrt 2 } – 2}}{{33 – 8\sqrt 2 + \sqrt {33 – 8\sqrt 2 } + 1}}\\
= \dfrac{{ – \sqrt {33 – 8\sqrt 2 } – 2}}{{\sqrt {33 – 8\sqrt 2 } + 34 – 8\sqrt 2 }}
\end{array}\)