If the matrix α−241−324−21 is non singular then α ∈
R
R−{−22}
R−{−24}
R{−26}
α−241−324−21≠0⇒α(−3+4)+2(1−8)+4(−2+12)≠0
α−14+40≠0α≠−26α∈R−{−26}