Mọi ng giúp em với Tìm x Question Mọi ng giúp em với Tìm x in progress 0 Môn Toán Nho 5 years 2020-11-04T04:16:05+00:00 2020-11-04T04:16:05+00:00 1 Answers 67 views 0
Answers ( )
Đáp án:
f. x=1
Giải thích các bước giải:
\(\begin{array}{l}
f.DK:x \ne 0\\
{x^8} = \dfrac{{{x^{12}}}}{{{x^5}}}\\
\to {x^8} = {x^4}\\
\to \dfrac{{{x^8}}}{{{x^4}}} = 1\\
\to {x^4} = 1\\
\to x = 1\\
g.\dfrac{{{x^{10}}}}{{{x^8}}} = 25\\
\to {x^2} = {5^2}\\
\to x = 5\\
h.\left| {x + 1} \right| + \left| {x + 2} \right| = 3x\\
\to \left[ \begin{array}{l}
x + 1 + x + 2 = 3x\left( {DK:x \ge – 1} \right)\\
– x – 1 + x + 2 = 3x\left( {DK: – 1 > x \ge – 2} \right)\\
x + 1 + x + 2 = – 3x\left( {DK: – 2 > x} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 3\left( {TM} \right)\\
x = \dfrac{1}{3}\left( l \right)\\
x = – \dfrac{3}{5}\left( l \right)
\end{array} \right.\\
i.\left| {x – 3} \right| + \left| {x – 5} \right| = 4x\\
\to \left[ \begin{array}{l}
x – 3 + x – 5 = 4x\left( {DK:x \ge 5} \right)\\
x – 3 – x + 5 = 4x\left( {DK:5 > x \ge 3} \right)\\
x – 3 + x – 5 = – 4x\left( {DK:3 > x} \right)
\end{array} \right.\\
\to \left[ \begin{array}{l}
2x = – 8\\
4x = 2\\
6x = 8
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = – 4\left( l \right)\\
x = \dfrac{1}{2}\left( l \right)\\
x = \dfrac{4}{3}\left( {TM} \right)
\end{array} \right.
\end{array}\)