NHANH VÀ ĐÚNG , TRÌNH BÀY ĐẦY ĐỦ = TICK NHA
B1 : Tìm x :
a. \(3.\left(2x-\dfrac{1}{2}\right)+2.\left(\dfrac{3}{8}-x\right)=2,75\)
b. \(x-\dfrac{1}{3}.\left(5-3x\right)=1\dfrac{1}{2}x+5\dfrac{1}{2}\)
c. \(\sqrt{x-1}=4\)
d. \(\left|x\right|-5\dfrac{3}{7}.\left|-x\right|-\dfrac{3}{4}=2.\left|x\right|-1\dfrac{1}{7}\)
e. \(x^2=8.\sqrt{x}\)(với x ≥ 0)
g) 3x+2 + 3x = 810
a)
\(3(2x-\frac{1}{2})+2(\frac{3}{8}-x)=2,75\)
\(\Leftrightarrow 6x-\frac{3}{2}+\frac{3}{4}-2x=2,75\)
\(\Leftrightarrow 4x=\frac{7}{2}\Rightarrow x=\frac{7}{8}\)
b)
\(x-\frac{1}{3}(5-3x)=1\frac{1}{2}x+5\frac{1}{2}\)
\(\Leftrightarrow x-\frac{5}{3}+x=x+\frac{1}{2}x+\frac{11}{2}\)
\(\Leftrightarrow \frac{1}{2}x=\frac{43}{6}\) \(\Rightarrow x=\frac{43}{3}\)
c) \(\sqrt{x-1}=4\Rightarrow x-1=4^2\Rightarrow x=4^2+1=17\)
d)
\(|x|-5\frac{3}{7}|-x|-\frac{3}{4}=2|x|-1\frac{1}{7}\)
\(\Leftrightarrow |x|-\frac{38}{7}|x|-\frac{3}{4}=2|x|-\frac{8}{7}\)
\(\Leftrightarrow |x|(1-\frac{38}{7}-2)=\frac{3}{4}-\frac{8}{7}\)
\(\Leftrightarrow |x|.\frac{-45}{7}=\frac{-11}{28}\)
\(\Leftrightarrow |x|=\frac{11}{180}\Rightarrow \left[\begin{matrix} x=\frac{11}{180}\\ x=-\frac{11}{180}\end{matrix}\right.\)
e)
\(x^2=8\sqrt{x}\)
\(\Leftrightarrow (\sqrt{x})^4=8\sqrt{x}\)
\(\Leftrightarrow \sqrt{x}[(\sqrt{x})^3-8)=0\)
\(\Leftrightarrow \left[\begin{matrix} \sqrt{x}=0\\ (\sqrt{x})=8=2^3\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=0\\ \sqrt{x}=2\end{matrix}\right.\)
\(\Rightarrow \left[\begin{matrix} x=0\\ x=4\end{matrix}\right.\)
