Perfect squares Polynomials

Algebra Level 3

$lx^2+mx+n \\ mx^2+nx+l \\ nx^2+lx+m$

For distinct non-zero values of $$l,m$$ and $$n$$. It is given that all of the algebraic expressios above are perfect square polynomials, find the value of $$\dfrac{l +m}n$$.

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