a) \( \lim{ \left( 4n^3+5n^2+n^4 \right) } = ? \)
b) \( \lim{ \left( 4n^3+5n^2-n^4 \right) } = ? \)
c) \( \lim{ \left( 5^n+6^n-7^n \right) } = ? \)
d) \( \lim{ \left( \sqrt{4n^6+3n^4}+\sqrt{5n^4+n^3} \right) } = ? \)
e) \( \lim{ \left( \sqrt{n^4-3n^2+5}-\sqrt{n^4+2n} \right) } = ? \)