Barry M. answered 12/19/19
Professor, CalTech Grad, with Years of Successful Tutoring Experience
This is linear, as expansion gives
y = 6x^2 - 6 - 6x^2
y = -6
This function is, therefore, a horizontal straight line and would be considered linear.
The linear term would be m in a general linear equation y = mx + b. In this case, m = 0.
The constant term is -6.