If  product of two roots of 4x3+16x2+kx−36=0  is –6 then k =

The given equation is f(x)=4x3+16x2+kx−36=0 Given that product of two roots (αβ)=−6And  αβγ=364⇒γ=−32Substitute x=−32  in f(x)⇒f(−32)=4(−32)3+16(−32)2+k(−32)−36=0After simplification, we get  k=−9