BÀI 4:
a) h(x) = f(x) - g(x)
h(x) = f(x) - g(x)= (x^4 - x^3 + 1) - (4 - 2x^3 + x^4 + 7x^5)
h(x) = f(x) - g(x)= x^4 - x^3 + 1 - 4 + 2x^3 - x^4 - 7x^5
h(x) = f(x) - g(x)= x^4 - x^4 - x^3 + 2x^3 + 1 - 4 - 7x^5
h(x) = f(x) - g(x)= x^3 + (-3) - 7x^5
=>h(x) = 7x^5 + x^3 - 3
b)f(-1)-g(-1)=(-1)^4-(-1)³+1-4+2.(-1)³-(-1)^4-7.(-1)^5
=1+1-4-2-1+7
=2
