Toán Tìm x. A) |x+1| / 8= 1/2. B) x/3-1/2=1/5 C) 11/8+13/6=85/x D) 4/2x+2=2x+2/9 27/09/2021 By Kennedy Tìm x. A) |x+1| / 8= 1/2. B) x/3-1/2=1/5 C) 11/8+13/6=85/x D) 4/2x+2=2x+2/9
Đáp án: d) \(\left[ \begin{array}{l}x = 2\\x = – 4\end{array} \right.\) Giải thích các bước giải: \(\begin{array}{l}a)\dfrac{{\left| {x + 1} \right|}}{8} = \dfrac{1}{2}\\ \to \left| {x + 1} \right| = 4\\ \to \left[ \begin{array}{l}x + 1 = 4\\x + 1 = – 4\end{array} \right.\\ \to \left[ \begin{array}{l}x = 3\\x = – 5\end{array} \right.\\b)\dfrac{x}{3} – \dfrac{1}{2} = \dfrac{1}{5}\\ \to \dfrac{x}{3} = \dfrac{7}{{10}}\\ \to x = \dfrac{{21}}{{10}}\\c)DK:x \ne 0\\\dfrac{{11}}{8} + \dfrac{{13}}{6} = \dfrac{{85}}{x}\\ \to \dfrac{{85}}{x} = \dfrac{{85}}{{24}}\\ \to x = 24\\d)DK:x \ne – 1\\\dfrac{4}{{2x + 2}} = \dfrac{{2x + 2}}{9}\\ \to {\left( {2x + 2} \right)^2} = 36\\ \to \left| {2x + 2} \right| = 6\\ \to \left[ \begin{array}{l}2x + 2 = 6\\2x + 2 = – 6\end{array} \right.\\ \to \left[ \begin{array}{l}x = 2\\x = – 4\end{array} \right.\end{array}\) Trả lời
Đáp án + giải thích bước giải : `a) |x + 1|/8 = 1/2` `-> |x + 1| . 2 = 8` `-> |x + 1| = 4` `-> x + 1 = 4` hoặc `x + 1 = -4` `-> x = 3` hoặc `x = -5` `b) x/3 – 1/2 = 1/5` `-> x/3 = 7/10` `-> 10x = 3. 7` `-> 10x = 21` `-> x =21/10` `c) 11/8 + 13/6 = 85/x` `-> 85/x = 85/24` `-> 85x = 85 . 24` `-> 85x = 2040` `-> x = 24` `d) 4/(2x + 2) = (2x + 2)/9` `-> 4 . 9 = (2x + 2) (2x + 2)` `-> (2x + 2)^2 = 36` `-> (2x + 2)^2 = 6^2` hoặc `(2x + 2)^2 = (-6)^2` `-> 2x + 2 = 6` hoặc `2x + 2 = -6` `-> 2x = 4` hoặc `2x = -8` `-> x = 2` hoặc `x = -4` Trả lời
Đáp án:
d) \(\left[ \begin{array}{l}
x = 2\\
x = – 4
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{{\left| {x + 1} \right|}}{8} = \dfrac{1}{2}\\
\to \left| {x + 1} \right| = 4\\
\to \left[ \begin{array}{l}
x + 1 = 4\\
x + 1 = – 4
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\\
x = – 5
\end{array} \right.\\
b)\dfrac{x}{3} – \dfrac{1}{2} = \dfrac{1}{5}\\
\to \dfrac{x}{3} = \dfrac{7}{{10}}\\
\to x = \dfrac{{21}}{{10}}\\
c)DK:x \ne 0\\
\dfrac{{11}}{8} + \dfrac{{13}}{6} = \dfrac{{85}}{x}\\
\to \dfrac{{85}}{x} = \dfrac{{85}}{{24}}\\
\to x = 24\\
d)DK:x \ne – 1\\
\dfrac{4}{{2x + 2}} = \dfrac{{2x + 2}}{9}\\
\to {\left( {2x + 2} \right)^2} = 36\\
\to \left| {2x + 2} \right| = 6\\
\to \left[ \begin{array}{l}
2x + 2 = 6\\
2x + 2 = – 6
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 2\\
x = – 4
\end{array} \right.
\end{array}\)
Đáp án + giải thích bước giải :
`a) |x + 1|/8 = 1/2`
`-> |x + 1| . 2 = 8`
`-> |x + 1| = 4`
`-> x + 1 = 4` hoặc `x + 1 = -4`
`-> x = 3` hoặc `x = -5`
`b) x/3 – 1/2 = 1/5`
`-> x/3 = 7/10`
`-> 10x = 3. 7`
`-> 10x = 21`
`-> x =21/10`
`c) 11/8 + 13/6 = 85/x`
`-> 85/x = 85/24`
`-> 85x = 85 . 24`
`-> 85x = 2040`
`-> x = 24`
`d) 4/(2x + 2) = (2x + 2)/9`
`-> 4 . 9 = (2x + 2) (2x + 2)`
`-> (2x + 2)^2 = 36`
`-> (2x + 2)^2 = 6^2` hoặc `(2x + 2)^2 = (-6)^2`
`-> 2x + 2 = 6` hoặc `2x + 2 = -6`
`-> 2x = 4` hoặc `2x = -8`
`-> x = 2` hoặc `x = -4`