Answer:
See below
Step-by-step explanation:
If an expression is not dependent on x, it simplified form must not contain x. To show that this is the case for (a) and (b) we need to simplify them and assess:
(a)
[tex](x-5)(x+8)-(x+4)(x-1)=\\=x^2-5x+8x-40-x^2-4x+x+4=-36[/tex]
Indeed, does not depend on x!
And (b)
[tex]x^4-(x^2-1)(x^2+1)=x^4-x^4+x^2-x^2+1=1[/tex]
Again, does not depend on x.
