(x+2)^2-x^2=16x=3原来的面积是9
2×2=4㎡16-4=12㎡12÷2=6㎡6÷2=3㎡3×3=9㎡
4X+4=16X=3面积为9
(x+2)^2 - x^2 = 164x + 4 = 16 , x = 3 , S = 3^2 = 9
