a/ P(x) = x - 2\(x^2+3x^{^{ }5}+x^4+x-1\)
= \(3x^5+x^4-2x^{^{ }2}+\left(x+x\right)-1\)
= 3\(x^{^{ }5}+x^4-2x^2+2x-1\)
Q(x) = \(-3x^5+3x^{^{ }4}+2x^2-2x+3\)
b/ P(x) = 3\(x^5+x^4-2x^{^{ }2}+2x-1\)
Q(x) = -3\(x^5+3x^4+2x^2-2x+3\)
P(x) +Q(x) = 4\(x^4+2\)
P(x) - Q(x) = 6x\(^5\)-2x\(^4\) - 4x\(^2\) + 4x - 4