Nope, because the area under the curve of -3x^2 is negative. And you are trying to find the total absolute area between two curves. Therefore (2-3x^2) becomes (-2+3x^2)
if you get a negative answer, that means your answer is wrong.
NOT -140
140 is the total area between the two curves, since the area under the x-axis is negative so you have to take into account for that.