Answer:
x^2 - 81
Step-by-step explanation:
There is a formula called the difference of squares, which is
(a+b)(a-b) = a^2 - b^2
the area of a trapezoid is
(b1 + b2)/2 × h = (10 + 5)/2 × 4 = 15 × 2 = 30 in²
