Hello Everybody!

I have a model y = 50+0.3*d-1*d*d+1.5*x+1.5*z-0.5*x*z-3.5*boy+u+5*rnormal() . All of my variables were generated from random variables and havebeen defined already. Boy is a binary variable.
I have been asked to find the joint the joint significance of variables x*z and d^2 interactions. I am not very sure what this means... To prove that they are both not equal to zero?

Thank you all for your input and have a great day.

A.