(5x-55).(x+20)=0 3(x-3)+6(x-1)=2 5(x-4)+2(x+7)=15 (x+3)(4x+8)=0 15/07/2021 Bởi Alexandra (5x-55).(x+20)=0 3(x-3)+6(x-1)=2 5(x-4)+2(x+7)=15 (x+3)(4x+8)=0
Đáp án: d. \(\left[ \begin{array}{l}x = – 3\\x = – 2\end{array} \right.\) Giải thích các bước giải: \(\begin{array}{l}a.\left( {5x – 55} \right)\left( {x + 20} \right) = 0\\ \to \left[ \begin{array}{l}5x – 55 = 0\\x + 20 = 0\end{array} \right.\\ \to \left[ \begin{array}{l}x = 11\\x = – 20\end{array} \right.\\b.3x – 9 + 6x – 6 = 2\\ \to 9x = 17\\ \to x = \dfrac{{17}}{9}\\c.5\left( {x – 4} \right) + 2\left( {x + 7} \right) = 15\\ \to 5x – 20 + 2x + 14 = 15\\ \to 7x = 21\\ \to x = 3\\d.\left( {x + 3} \right)\left( {4x + 8} \right) = 0\\ \to \left[ \begin{array}{l}x + 3 = 0\\4x + 8 = 0\end{array} \right.\\ \to \left[ \begin{array}{l}x = – 3\\x = – 2\end{array} \right.\end{array}\) Bình luận
Đáp án:
d. \(\left[ \begin{array}{l}
x = – 3\\
x = – 2
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\left( {5x – 55} \right)\left( {x + 20} \right) = 0\\
\to \left[ \begin{array}{l}
5x – 55 = 0\\
x + 20 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = 11\\
x = – 20
\end{array} \right.\\
b.3x – 9 + 6x – 6 = 2\\
\to 9x = 17\\
\to x = \dfrac{{17}}{9}\\
c.5\left( {x – 4} \right) + 2\left( {x + 7} \right) = 15\\
\to 5x – 20 + 2x + 14 = 15\\
\to 7x = 21\\
\to x = 3\\
d.\left( {x + 3} \right)\left( {4x + 8} \right) = 0\\
\to \left[ \begin{array}{l}
x + 3 = 0\\
4x + 8 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = – 3\\
x = – 2
\end{array} \right.
\end{array}\)