\(\Delta'=4a^2b^2-\left(a^2+b^2-c^2\right)^2=\left(2ab-a^2-b^2+c^2\right)\left(2ab+a^2+b^2-c^2\right)\)
\(=\left(c^2-\left(a-b\right)^2\right)\left(\left(a+b\right)^2-c^2\right)\)
\(=\left(c+a-b\right)\left(c-a+b\right)\left(a+b+c\right)\left(a+b-c\right)>0\)
=> pt luôn có 2 nghiệm pb .