I am currently practicing questions on Green's Theorem however in some questions I have been given a finite region enclosed between a parabola and a horizontal line. In these questions I am given 2 values of y but none of x. In one question I was given that y = x^2 and y = 9 and was immediately able to spot that x satisfies this for the values -3 and 3 therefore x [-3,3] and y [ x^2, 9] However I now have come across a situation where y = 3x^2 and y = 5 and I cannot seem to spot any sort of relationship between these 2. Based on previous questions I figured these values of x would satisfy both values of y given. Can anybody tell me how these limits are established? I've integrated in terms of y and now have all x terms but do not know what limits to apply to the integral.