Question

the area of the trapezoid is (3/4x-1/4) square centimeters. two pairs of expressions that represent possible lengths of bases. height is 1/2 centimeters

Answer 1

Let a and be be the bases. 
The formula of the area is the following :
$\frac{a+b}{2}\times h= \frac{a+b}{2}\times\frac{1}{2}=\frac{a+b}{4}$
Equating we get the equation:
$\frac{a+b}{4} = \frac{3}{4} x- \frac{1}{4} = \frac{3x+1}{4}$
So, identifying we get two possible expression:
$a=3x,b=1$