The sides of a triangle are x^{2} – 3xy + 8, 4x^{2} + 5xy – 3 and 6 – 3x^{2} + 4xy. Find its perimeter.
Required perimeter = Sum of three sides
= x^{2} – 3xy + 8 + 4x^{2} + 5xy – 3 + 6 – 3x^{2} + 4xy
= x^{2} + 4x^{2} – 3x^{2} – 3xy + 5xy + 4xy + 8 – 3 + 6
= 2x^{2} + 6xy + 11