Answer:
3rd side = 6x + 3
Step-by-step explanation:
The perimeter must be the given trinomial
The 3rd side = Perimeter - sum of the two given sides.
side 1 = 4x^2 + 2x
side 2 = 3x^2 + 6
Sum = 7x^2 + 2x + 6
3rd side = Perimeter - sum
3rd side = 7x^2 + 8x + 9 - (7x^2 + 2x + 6) Remove the brackets
3rd side = 7x^2 + 8x + 9 - 7x^2 - 2x - 6
3rd side = 6x + 3
