The area of a rectangle is given by the next equation:
Area = Length * Width
Where
Length =1/2x²+2x+4.
and
Width = 3x−1
Replacing:
Area = (1/2x²+2x+4)* (3x-1)
Solve the operation:
(1/2x²* 3x) + (1/2x²*-1)+(2x*3x)+(2x*-1)+(4*3x)+(4*-1)
Simplify:
3/2x³-1/2x²+6x²-2x+12x-4
= 3/2x³+11/2x²+10x-4
Hence, the correct answer is a(x)=3/2x³+11/2x²+10x-4