mình ghi thiếu b , căn x + 9 <= 31
so sánh : -3 căn3 và -2 căn7
\(\sqrt{-2x+1}>7\)
<=> -2x + 1 > 72
<=> -2x > 49 - 1
<=> -2x > 48
<=> -2x : (-2) > 48 : (-2)
<=> x < -24
\(a) Đk:x<\dfrac{1}{2}\)
\(\sqrt{-2x+1}>7\)
\(\Leftrightarrow\)\(-2x+1>49\)
\(\Leftrightarrow\)\(x<-24\)
\(b)\)\(Đk:x>-9\)
\(\sqrt{x+9}\)\(\le\)\(31\)
\(\Leftrightarrow\)\(x+9\)\(\le\)\(961\)
\(\Leftrightarrow\)\(x\)\(\le\)\(952\)
\(c)\)Ta có:
\(-3\sqrt{3}=-\sqrt{27} \)
\(-2\sqrt{7}=-\sqrt{28}\)
\(-\sqrt{27}>-\sqrt{28}\)
\(\Rightarrow\)\(-3\sqrt{3}>-2\sqrt{7}\)
