Bài 5:
\(a.\dfrac{2x-1}{5}-\dfrac{x-2}{3}=\dfrac{x+7}{15}\\ \Leftrightarrow\dfrac{3\left(2x-1\right)}{15}-\dfrac{5\left(x-2\right)}{15}=\dfrac{x+7}{15}\\ \Leftrightarrow3\left(2x-1\right)-5\left(x-2\right)=x+7\\ \Leftrightarrow6x-3-5x+10=x+7\\ \Leftrightarrow x+7=x+7\\ \Leftrightarrow0=0\)
=> Pt vô số nghiệm
\(b.\dfrac{x+2}{2}-\dfrac{x-1}{3}=\dfrac{x+5}{6}+1\\ \Leftrightarrow\dfrac{3\left(x+2\right)}{6}-\dfrac{2\left(x-1\right)}{6}=\dfrac{x+5}{6}+\dfrac{6}{6}\\ \Leftrightarrow3\left(x+2\right)-2\left(x-1\right)=x+5+6\\ \Leftrightarrow3x+6-2x+2=x+11\\ \Leftrightarrow x+8=x+11\\ \Leftrightarrow8=11\)
=> Phương tình vô nghiệm
\(c.\dfrac{2\left(x+5\right)}{3}+\dfrac{x+12}{2}-\dfrac{5\left(x-2\right)}{6}=\dfrac{x}{3}-+11\\ \Leftrightarrow\dfrac{4\left(x+5\right)}{6}+\dfrac{3\left(x+12\right)}{6}-\dfrac{5\left(x-2\right)}{6}=\dfrac{2x}{6}+\dfrac{66}{6}\\ \Leftrightarrow4\left(x+5\right)+3\left(x+12\right)-5\left(x-2\right)=2x+66\\ \Leftrightarrow4x+20+3x+36-5x+10=2x+66\\ \Leftrightarrow2x+66=2x+66\\ \Leftrightarrow0=0\)
=> Pt vô số nghiệm
