Circle a has a radius of (x + 4) units. a larger circle, b, has a radius of (x + 6) units.

part 1: use the formula acircle=πr^2
to write a single expression for the difference in the areas of the circles. (in that formula, "r" stands for "radius".) simplify your expression as much as possible (by doing things such as combining like terms), but leave your answer in terms of x and π.

part 2: after you've found a general formula for the difference between those circles (in part 1), approximate to the nearest whole number the difference in the areas in the specific case when x = 12. (you can approximate π as 3.14 in part 2.)

show all of your mathematical steps clearly. explain and justify your work using complete sentences.