a/\(\Leftrightarrow\left(a^2+b^2\right)x+2abx-\left(a+b\right)=0\)
\(\Leftrightarrow x\left(a^2+b^2+2ab\right)-\left(a+b\right)=0\)
\(\Leftrightarrow\left(a+b\right)^2x-\left(a+b\right)=0\)
\(\Leftrightarrow\left(a+b\right)\left(ax+bx-1\right)=0\)
Để PT vô số nghiệm thì a=-b
b/