Question

Answer 1

\(\Leftrightarrow21.\left(x+1\right)=15.\left(x-5\right)\\ \Leftrightarrow21x+21=15x-75\\ \Leftrightarrow21+75=15x-21x\\ \Leftrightarrow96=-6x\\ \Leftrightarrow x=-\dfrac{96}{6}=-16\)

Vậy pt có nghiệm S = -16

Answer 2

\(\Rightarrow21\times\left(x+1\right)=15\times\left(x-5\right)\)

\(\Rightarrow21x+21=15x-75\)

\(\Rightarrow21+75=15x-21x\)

\(\Rightarrow96=-6x\)

\(\Rightarrow x=-\dfrac{96}{6}=-16\)

Vậy PT có nghiệm S= -16