If  the product of two roots of x3+kx2−3x+4=0  is –1, then k =

The given equation is x3+kx2−3x+4=0 Let α,β,γ are the roots of given equationGiven  that, product of two roots = -1i.e ,  αβ=−1   s3=αβγ=−4 ⇒  γ=4 ∴   4 is one root of the given equation⇒f(4)=0 ⇒  (4)3+k(4)2−3(4)+4=0 ⇒k=−72