Question

What are the domain and range of the function f(x)= x^4 -6x^3 -4x^2 54x -45?

Answer 1

Domain is the numbers you can use
we can use all real numbers for this one

rangge is the numbers we get from inputting the domain

well, this is a 4th degree, so we need to find the minimum,because the leading coefient is positive so it opens up, and as x approaches negative and positive infinity, then f(x) approaches infnity

find minimum
take derivitive
f'(x)=4x^3-18x^2-8x+54
the zeroes are at about -1.652 and 1.9381 and 4.2145
we use a sign chart
the minimum occurs at hwere the derivitive changes from negative to positive
that is at -1.652 and 4.2145
evaluate f(-1.652) and f(4.2145)
f(-1.652)=-110.626
f(4.2145)=-22.124
the least value is -110.626
that is the minimum

so the domain is all real numbers
range is from -110.626 to infinity