Answer:
SA = 16x^2 +30x+6
Step-by-step explanation:
The surface area is given by
SA = 2 (lw + lh + wh)
The length is 2x, the width is (x+3) and the height is (2x+1)
SA = 2 ((2x)*(x+3) + (2x)*(2x+1) + (x+3) (2x+1))
We need to distribute
SA = 2 ((2x^2+6x) + (4x^2+2x) + (2x^2 +6x+x+3))
Combine like terms
SA = 2 (2x^2+ 4x^2+2x^2+6x+2x +6x+x+3)
SA = 2 (8x^2+15x+3)
Multiply by 2
SA = 16x^2 +30x+6
