Bài 1: Tìm x, bt
a) 5\12.|x|=10\3
b) 7\3 – 2.|x|= 1,5
c) |4 – x| \2và3\5=-3\5
d) |x-1\2| + 5 = 14,5
Bài 1: Tìm x, bt a) 5\12.|x|=10\3 b) 7\3 – 2.|x|= 1,5 c) |4 – x| \2và3\5=-3\5 d) |x-1\2| + 5 = 14,5
By Genesis
By Genesis
Bài 1: Tìm x, bt
a) 5\12.|x|=10\3
b) 7\3 – 2.|x|= 1,5
c) |4 – x| \2và3\5=-3\5
d) |x-1\2| + 5 = 14,5
Giải thích các bước giải:
a) $\frac{5}{12}$ . | x | = $\frac{10}{3}$
→ | x | = $\frac{10}{3}$ . $\frac{12}{5}$
→ | x | = 8
→\(\left[ \begin{array}{l}x=8\\x=-8\end{array} \right.\)
Vậy x ∈ { ± 8 }
b) $\frac{7}{3}$ – 2 . l x l = 1,5
→ $\frac{7}{3}$ – 2 . l x l = $\frac{3}{2}$
→ 2 . | x | = $\frac{7}{3}$ – $\frac{3}{2}$
→ 2 . | x | = $\frac{5}{6}$
→ | x | = $\frac{5}{6}$ . $\frac{1}{2}$
→ | x | = $\frac{5}{12}$
→ \(\left[ \begin{array}{l}x=5/12\\x=-5/12\end{array} \right.\)
Vậy x ∈ { ± $\frac{5}{12}$ }
c) $\frac{|4 – x|}{2}$ + $\frac{3}{5}$ = $\frac{-3}{5}$
→ |4 – x| . $\frac{1}{2}$ = $\frac{-3}{5}$ – $\frac{3}{5}$
→ |4 – x| = $\frac{-6}{5}$ . 2
→ |4 – x| = $\frac{-12}{5}$ ( loại )
d) | $\frac{x}{1/2}$ | + 5 = 14,5
→ | $\frac{x}{1/2}$ | = $\frac{19}{2}$
→\(\left[ \begin{array}{l}x- 1/2 = 19 /2\\x-1/2=-19/2\end{array} \right.\)
→ \(\left[ \begin{array}{l}x=10\\x=-9\end{array} \right.\)
Vậy x ∈ { 10 ; -9 }
Đáp án:
d) \(\left[ \begin{array}{l}
x = 10\\
x = – 9
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{5}{{12}}.\left| x \right| = \dfrac{{10}}{3}\\
\to \left| x \right| = 8\\
\to \left[ \begin{array}{l}
x = 8\\
x = – 8
\end{array} \right.\\
b)\dfrac{7}{3} – 2\left| x \right| = \dfrac{3}{2}\\
\to 2\left| x \right| = \dfrac{5}{6}\\
\to \left| x \right| = \dfrac{5}{{12}}\\
\to \left[ \begin{array}{l}
x = \dfrac{5}{{12}}\\
x = – \dfrac{5}{{12}}
\end{array} \right.\\
d)\left| {x – \dfrac{1}{2}} \right| + 5 = \dfrac{{29}}{2}\\
\to \left| {x – \dfrac{1}{2}} \right| = \dfrac{{19}}{2}\\
\to \left[ \begin{array}{l}
x – \dfrac{1}{2} = \dfrac{{19}}{2}\\
x – \dfrac{1}{2} = – \dfrac{{19}}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 10\\
x = – 9
\end{array} \right.
\end{array}\)
( câu c đề không rõ ràng b nhé )