Answer:
perimeter = 7x² + 7y² + 4y - 3x
Explanation:
the perimeter (P) is the sum of the 3 sides of the triangle , that is
P = 3x² - y² + 4x² - 7xy + 4y - 3x + 7xy + 8y² ← collect like terms
= (3x² + 4x²) + (- y² + 8y²) + (- 7xy + 7xy) + 4y - 3x
= 7x² + 7y² +0 + 4y - 3x
= 7x² + 7y² + 4y - 3x