lf α,β are the roots of the equation x2+mx+l=0 and γ,δ that of x2+nx+l=0, then the value of (α−γ)(β−γ)(α−δ)(β−δ)=
A
l(m+n)2
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B
−l(m+n)2
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C
l(m−n)2
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D
1(m+n)
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Solution
The correct option is Cl(m−n)2 (α−γ)(β−γ)=αβ−(α+β)γ+γ2 ...(1) (α−δ)(β−δ)=αβ−(α+β)δ+δ2 ...(2) α+β=−m;αβ=l;γ+δ=−n;γδ=l ∴αβ=γδ=l l+γ2=−nγ and l+δ2=−nδ ...(3) Substituting the roots in the second equation From (1), (2), and (3), we get (α−γ)(β−γ)(α−δ)(β−δ)=(l+mγ+γ2)(l+mδ+δ2) =(m−n)2γδ =(m−n)2l