an equation which contain solutions independent and not equal to zero
like
a1b1+a2b2+.....=0
in this equation
a1b1 is independent from a2b2 ( this can be proved from wronskian theorem )
wronskian
w= det(a1b1,a2b2/d(a1b1)d(a2b2))
also
a1b1, a2b2 not equal to zero