Toán Lớp 6: tìm số nguyên X, biết : a, x+1/5=x+3/10 ; b, x+1/5=5/x+1
c, x/4=18/x+1
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Toán Lớp 6: tìm số nguyên X, biết : a, x+1/5=x+3/10 ; b, x+1/5=5/x+1
c, x/4=18/x+1
Comments ( 1 )
Giải đáp:
\(\begin{array}{l}
a)x = 1\\
b)\left[ \begin{array}{l}
x = 4\\
x = – 6
\end{array} \right.\\
c)\left[ \begin{array}{l}
x = – 9\\
x = 8
\end{array} \right.
\end{array}\)
Lời giải và giải thích chi tiết:
\(\begin{array}{l}
a)\dfrac{{x + 1}}{5} = \dfrac{{x + 3}}{{10}}\\
\to 2x + 2 = x + 3\\
\to x = 1\\
b)DK:x \ne – 1\\
\dfrac{{x + 1}}{5} = \dfrac{5}{{x + 1}}\\
\to {\left( {x + 1} \right)^2} = 25\\
\to \left| {x + 1} \right| = 5\\
\to \left[ \begin{array}{l}
x + 1 = 5\\
x + 1 = – 5
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 4\\
x = – 6
\end{array} \right.\\
c)DK:x \ne – 1\\
\dfrac{x}{4} = \dfrac{{18}}{{x + 1}}\\
\to x\left( {x + 1} \right) = 4.18\\
\to {x^2} + x – 72 = 0\\
\to {x^2} + 9x – 8x – 72 = 0\\
\to x\left( {x + 9} \right) – 8\left( {x + 9} \right) = 0\\
\to \left( {x + 9} \right)\left( {x – 8} \right) = 0\\
\to \left[ \begin{array}{l}
x = – 9\\
x = 8
\end{array} \right.
\end{array}\)