Answer:
6x² + 36x + 22
Step-by-step explanation:
2 faces (x + 3) by (x + 7), area of both these faces 2(x+3)*(x + 7)
2 faces (x + 3) by (x - 1), area of both these faces 2(x+3)*(x - 1)
2 faces (x -1 ) by (x + 7), area of both these faces 2(x-1)*(x + 7)
Whole surface area is
2(x+3)*(x + 7) + 2(x+3)*(x - 1) + 2(x-1)*(x + 7) =
=2(x² + 3x +7x +21) + 2(x² +3x -x - 3) + 2(x² - x +7x -7)=
=2x² + 20x +42 + 2x² + 4x - 6 + 2x² + 12x -14 =
= 6x² + 36x + 22
