Why is the graph method of finding area not considered 100% accurate?

Rohit is trying to tune an instrument

The temperature at a point (x, y) is t(x, y), measured in degrees celsius. a bug crawls so that its position after t seconds is given by x = 6 + t , y = 8 + 1 3 t, where x and y are measured in centimeters. the temperature function satisfies tx(3, 9) = 5 and ty(3, 9) = 4. how fast is the temperature rising on the bug's path after 3 seconds? (round your answer to two decimal places.)

Infrared radiation has wavelengths that are shorter than visible light is part of the visible light spectrum has wavelengths that are longer than visible light has the same wavelengths as ultraviolet radiation