Giải : B = [căn x/(căn x+3)]+[(2 căn x)/căn x-3)]-[(3 căn x+9)/(x-9)] 07/08/2021 Bởi Everleigh Giải : B = [căn x/(căn x+3)]+[(2 căn x)/căn x-3)]-[(3 căn x+9)/(x-9)]
Đáp án: \(\dfrac{{3x – 9}}{{x – 9}}\) Giải thích các bước giải: \(\begin{array}{l}DK:x \ge 0;x \ne 9\\B = \dfrac{{\sqrt x }}{{\sqrt x + 3}} + \dfrac{{2\sqrt x }}{{\sqrt x – 3}} – \dfrac{{3\sqrt x + 9}}{{x – 9}}\\ = \dfrac{{\sqrt x \left( {\sqrt x – 3} \right) + 2\sqrt x \left( {\sqrt x + 3} \right) – 3\sqrt x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\ = \dfrac{{x – 3\sqrt x + 2x + 6\sqrt x – 3\sqrt x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\ = \dfrac{{3x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\ = \dfrac{{3x – 9}}{{x – 9}}\end{array}\) Bình luận
Đáp án:
\(\dfrac{{3x – 9}}{{x – 9}}\)
Giải thích các bước giải:
\(\begin{array}{l}
DK:x \ge 0;x \ne 9\\
B = \dfrac{{\sqrt x }}{{\sqrt x + 3}} + \dfrac{{2\sqrt x }}{{\sqrt x – 3}} – \dfrac{{3\sqrt x + 9}}{{x – 9}}\\
= \dfrac{{\sqrt x \left( {\sqrt x – 3} \right) + 2\sqrt x \left( {\sqrt x + 3} \right) – 3\sqrt x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\
= \dfrac{{x – 3\sqrt x + 2x + 6\sqrt x – 3\sqrt x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\
= \dfrac{{3x – 9}}{{\left( {\sqrt x + 3} \right)\left( {\sqrt x – 3} \right)}}\\
= \dfrac{{3x – 9}}{{x – 9}}
\end{array}\)
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