Question of the Day 18-11-2019

Question of the Day
GATE 2017   CE   Question No. 20

Consider the following partial differential equation:

$\style{font-family:'Times New Roman'}{3\frac{\partial^2\phi}{\partial x^2}+B\frac{\partial^2\phi}{\partial x\partial y}+3\frac{\partial^2\phi}{\partial y^2}+4\phi=0}$

For this equation to be classified as parabolic , the value of B2 must be _____________.