Answer:
P = 10x³ + 4x² + 8x + 6
Step-by-step explanation:
The perimeter of a rectangle is twice the sum of length and width.
P = 2(L+W) = 2((x³ +2x² -6x +12) +(4x³ +10x -9))
= 2(5x³ +2x² +4x +3) . . . . collect terms inside parentheses
P = 10x³ +4x² +8x +6
