If the product of two roots of x3+kx2+31x−30=0  is 15, then k=

The given equation is x3+kx2+31k−30=0 Let the roots are α,β,γ Then product of the roots : αβγ=30 By the given condition , the product of the two roots  αβ=15 ⇒15γ=30  ⇒γ=2 γ=2  is the one root of given equation⇒8+4k+62−30=0 ⇒4k+40=0 ∴ k=−10 Hence (3) is correct choice.