đk x > = 0 ; x khác 9 ; 64
a, Thay vào ta được
\(P=\left(\dfrac{4}{4+3}-\dfrac{2\left(4+12\right)}{16-9}\right).\dfrac{4+5}{4-8}=\left(\dfrac{4}{7}-\dfrac{32}{17}\right).\dfrac{9}{-4}\)
\(=-\dfrac{9}{7}+\dfrac{72}{17}=\dfrac{351}{119}\)
b, \(P=\left(\dfrac{\sqrt{x}\left(\sqrt{x}-3\right)-2\sqrt{x}-24}{x-9}\right).\dfrac{\sqrt{x}+5}{\sqrt{x}-8}\)
\(=\dfrac{x-5\sqrt{x}-24}{x-9}.\dfrac{\sqrt{x}+5}{\sqrt{x}-8}=\dfrac{\sqrt{x}+5}{\sqrt{x}-3}\)
c, Ta có \(P-1=\dfrac{\sqrt{x}+5}{\sqrt{x}-3}-1=\dfrac{8}{\sqrt{x}-3}\le0\Rightarrow\sqrt{x}-3< 0\Leftrightarrow x< 9\)
Kết hợp đk vậy 0 =< x < 9
Đúng 1
Bình luận (0)
