Y=2x-9x евляется ли эта функция линейной

No, this function is not linear. A linear function has a form of y = mx + b, where m is the slope and b is the y-intercept. In this case, the function y = 2x - 9x can be simplified to y = -7x, which is a linear function with a slope of -7 and no y-intercept.