Question

Which on eof the following functions can have negative values?

a)y=6x^2+4
b)y=|5x+4|
c)y=4x^4+x^2
d)y=(x-2)^3

Answer 1

This question is best answered with a sketch of each function.

For example, a, b, and c have V-shaped graphs, i.e. the tails at x=-∞ and at x=∞ are pointing upwards.
The left tail of d) points downwards, and the right tail upwards.
Convince yourself of these shapes and do a little sketch for each to confirm your answer.