Given that, x3+px2−qx+r=0 . . . (i) Let α,β,γ are roots of this equation ‌α+β+γ=−p . . . (ii) αβ+βγ+γα=−q. . . (iii) ‌ and ‌‌‌‌αβγ=−r . . . (iv) Now =‌(0+β+γ)(αβ+γ(α+β)) ‌=(0+γ)(αβ+γ(α+β)) ‌‌‌‌‌[∴α+β=0‌ given ‌] =‌γ(αβ+0)=αβγ=−r