\(4(x-3)+5(x+3)=45\\ → 4x-12+5x+15 =45 → 9x=42 \\ → x=\dfrac{14}{3}\)
Vậy \(x=\dfrac{14}{3}\).
\(4(x-3)+5(x+3)=45 \\ \Leftrightarrow 4x-12+5x+15=45 \\ \Leftrightarrow 4x+5x=45+12-15 \\ \Leftrightarrow 9x=42 \\ \Leftrightarrow x=42:9 \\ \Leftrightarrow x=\dfrac{42}{9} =\dfrac{14}{3}\)
4.(x-3)+5.(x+3)=45
4x-12+5x+15=45
9x=42
x=\(\dfrac{42}{9}\)
x=\(\dfrac{14}{3}\)