\(\widehat{A}+\widehat{B}\) = 210o => \(\widehat{A}\) = 210o - \(\widehat{B}\)
\(\widehat{B}+\widehat{C}\) = 216o => \(\widehat{C}\) = 216o - \(\widehat{B}\)
\(\widehat{C}+\widehat{D}\) = 150o => \(\widehat{D}\) = 150o - \(\widehat{C}\) = 150o - (216o - \(\widehat{B}\)) \(\widehat{B}\) - 66o
\(\widehat{A}+\widehat{B}+\widehat{C}+\widehat{D}=360^o\)
\(210^o-\widehat{B}+\widehat{B}+216^o-\widehat{B}+\widehat{B}-66^o=360^o\)
=> Hệ số vô nghiệm