Question

Giải pt: a(a-5) - 2(a-5)a = 18

Answer 1

\(a\left(a-5\right)-2\left(a-5\right)a=18\)

\(\Leftrightarrow a^2-5a-2a^2+10a-18=0\)

\(\Leftrightarrow-a^2+5a-18=0\)

\(\Delta=b^2-4ac=5^2-4.\left(-1\right).\left(-18\right)=-72< 0\)

\(\Leftrightarrow\)pt vô nghiệm 

Vậy \(S=\varnothing\)

 

Answer 2

\(a\left(a-5\right)-2a\left(a-5\right)=18\)

\(a^2-5a-2a^2+10a=18\)

\(-a^2+5a-18=0\)

Ta có: \(\text{∆}=5^2-4.18=-47\)

Vì ∆<0 => pt vô nghiệm